Welcome to English in a Minute.
If you ever heard people saying goodbye in American English, you probably have heard this: Make sure to stay in touch.
People who don't see each other often like to find ways to "stay in touch." But waht does that mean?
A: It was great to see you at the class reunion. Now make sure to stay in touch. I want to talk to you before our next reunion.
B: I will. I'll stay in touch, and I'll call you sometimes next week.
"stay in touch" or "keeping in touch" says that you want to communicate with someone. It means you want to keep in contact, maybe by phone or email -- even though you don't see that person often.
Make sure to stay in touch.
And that's English in a Minute.