Info on spawning an item via command?

Hello

i have been looking into plugins lately running my own server
and i wanted to make a plugin that via a command takes certain resource and gives back a item
but also checks this the player using the command has enough resources

now i couldnt really find anything in the api about giving and taking items from players
and was wondering if theres a document somewhere with more info about commands/functions
or am i looking over something hope someone can point me in the right direction