Server and its ristriction

Hello,
hy i m very begennir . so i want to know what is server and how does it works. and i also want to know that how can i attach my to my friend pc that i can intyerrupt and able to give damage to him on the same local are networking. we are using cat 6 wire. so descibe me deeply . what should i do. and i jst want to told u that i want hack others pc. i tried many tricks bt non of them work correctly ..



plz help me