Speaking the same language as your audience is important. In most cases you're already speaking the literal, high-level language of your audience but it's a lot more nuanced than that. Language at a lower level is one thing that trips people up on the way to understanding. Jargon, acronyms, slang, and cultural quirks can all act as barriers to mutual understanding - which is the whole reason we communicate. These are so ingrained in us, however, that it takes effort to suppress them. First though, you have to know what they are.
If you're an expert, if you're deep into your field, your language is so ingrained that you likely can't identify all of things you say that others won't understand.
We know a finite number of languages. We have the capacity to learn more but we have to put in the work. When you start a new job or join a new group, it takes time to learn and internalize that new language. So how do we go about learning a new language or translating our message into the proper language for our audience? Even if it's a one-time engagement, your message will be more successful if it's in terms your audience doesn't have to Google.
Learning and embodying the language of your audience is one of the things that drew me to public relations. When done well, PR stands between two groups and acts as a bridge for mutual understanding. So here are some pointers on how to reap the benefits of shared language even if you aren't totally fluent in your audience's language.
The goal is to meet in the middle by using their language and clarifying yours when needed.
If you're presenting at a conference outside of your field or at an organization, read the organization or conference's promotional material. Read the mission statement, employee bios, product descriptions, anything that they've written and use to tell people who they are. That might give you a starting vocabulary. You'll at least be able to pick out their buzzwords and might find a few that you need to Google.
If you have the time and inclination to do a little more research, you can find sources that will resonate with your audience - sources with which they're already familiar. I used to do an exercise with my public speaking classes to identify proper sources for given audiences - not every source will work for every audience. Is there a well-known expert that you can reference as a hat-tip? Are there sources/names/misconceptions you should avoid? If you can show that you've done your research and speak their language, you have a chance earning some extra respect and trust from your audience, in addition to increasing your chances of persuasion/education.
For translating yourself, think about which words or phrases your audience might not understand - decide whether they should be replaced or defined. Then, get an outside opinion. Get the person you know with the least familiarity with the subject read through or listen to your content and ID words or phrases that they don't understand. I'm happy to be this person - drop me an email or DM. If you know someone who is a member of you target audience, even better. Err on the side of caution. This doesn't mean that you have to cut every piece of jargon or every specialized phrase but it's hard to know what your audience won't know when you're so embedded in the content. We take language for granted because we use it all of the time.
When jargon or initialism is important, define it the first time you use it. If you have a powerpoint, put the definition/explanation on the slide. If it's a long talk, remind people what it means later on. If it's a particularly slippery term (if they might have a misconception about the term or if it's just really strange) keep the definition on your slides whenever you're using it.
If the jargon or initialism or what-have-you is not critical for understanding, I recommend not using it. There are many exceptions to this but, if your goal is that your audience easily understands your message, you might need to replace some terms. Honestly, critically, think about which words you need to make your audience grasp the point. Get the friend who identified the terms to help you replace them with something more understandable. The thesaurus is a wonderful resource, too.
If you're familiar with open-source intelligence (OSINT) or social engineering (SE) these tactics are probably familiar to you but if that's not your area of expertise, I hope you find these useful in your efforts to work with people and reach understanding. You're trying to weave your language with theirs to help them learn something new.
A note on analogies: I'm always cautious when it comes to analogies in information security. People try to make analogies a perfect fit and they rarely are for infosec which can lead to frustration, misconceptions, bad things. However, this article on CSO by J.M. Porup has some actually useful guidelines on using analogies. If you follow those pointers and find an analogy that is a good fit for your audience, this can be another useful way to connect the dots for your audience.
Hopefully, you can use these tactics to reach a shared understanding with your audience a little more easily. The key first step for this is motivation - you have to want to do the work to make your talk accessible. You have to respect your audience's knowledge, even if it's different from your own. From what I can tell, this isn't something people reading my blog need to be told but, it's worth saying.