I need some helps on geminis (yugioh)?

Okay i need help so from what i know i can normal summon with out sacrafising any monsters for a lvl 5 or higher monster and when there on the field instead of normal summoning i can activate the effect by re summoning or does he have to go to my grave yard or hand to do so please tell me cause that might mean i have been using my ill blud wrong :) please ant shank you