What are the random pictures on my instagram?

Okay so on my iphone, the instagram app has all these random pictures of other people that I don't know that are on the star looking screen- I was wondering if that was other instagram users and that means that somebody elses instagram might have my picture on there sometimes. If this is the case, is there a way I can make mine not be up there? Also, while I'm at it, I keep getting texts from friends with a lot of extra punctuation- i could… Get a text… That looks like… Thissssss- is there any meaning to all of that? I would say the age range of these people is probably like 22-40 and I'm 27 myself so I was thinking it might be one of those things the whole world knows about except for me haha.

"Star looking screen" do you mean the second button from the left? That shows other people's pictures that have TONS of likes. For example, most celebraties are shown on that page and other slightly famous people/ or youtubers because they get like 42093 likes on a photo. Your photo will not appear on there unless you get a huge amount of likes, and if your not famous or have a lot of followers, you don't really have anything to worry about.
For the text thing, i know my friends and i text like thisss sometimes when we try to get a point across.
Example: Hey wanna go shopping?
Me: yes… I doo
why do we do this? Because a simple yes does not cover it.
If this is not the reason why they text you that way, then sorry i have to idea why they put extra punctuation, but yeah, lol