Based on your other posts, it looks like you are asking about going through customs on your upcoming trip from the US to Mombasa back to the US.

In Kenya you will hopefully have no goods to declare and should just be waved through.

Coming back to the US, you may be asked a few questions at passport control. Usually they will at least ask "where are you coming from" and "how long have you been gone" and "did you bring back any food?" If you are young and someone who hasn't travelled a lot internationally, they may also ask you why you were in Kenya, what you do for a living, and, importantly, who paid for the trip.

If you answer, "I'm an artist/musician/hippie and my trip to Kenya was paid for by a shady Nigerian guy I met in a nightclub in the US last week," they are probably going to ask a lot more questions to determine if you are a drug mule.

If you explain that you have a respectable job, you paid for the ticket yourself, or it was a church trip, etc., then they will probably wave you through.

I note that your other post suggests you might fly KLM. If you go through Amsterdam, be prepared for a lot of questions from Amsterdam ground staff. They are very polite but very thorough asking passengers why were you in Amsterdam, who you are traveling with, where you went, who paid for your trip, whether you own the items in your bags, etc. Looking for terrorists and drug smugglers, I suppose.

Have you ever seen the show "Locked Up Abroad" on the National Geographic channel? Check it out, it's good and will give you fun nightmares before your trip to Mombasa.

Good luck.