wordpress plugin example sample code

Hi, I’m trying to learn PHP and write a plugin for my own wordpress site https://alexus.org/. I’m trying to understand how I can pass a parameters through a post to my plugin and call plugin overall. I’m reading documentations and so far between me not knowing php all that well and trying to understand this new API I can’t really connect dots, can someone describe a very simple plugin or perhaps show an example or maybe a webpage where such example describes in details? sorry if it’s too n00b;p