Are you asking for a definition of Gravity? Well its a constant force that is applied to objects within the game loop.
In a simple example inside the main loop you might have a sprite (2d) like so:
"Gravity" can be applied to the YAxis using the following in the Game loop:
This will increase the YPos by 1 every time the game loops, effectively pushing the sprite down.
A forum search would give you more than enough information you need. Search either "Gravity" or "Jumping".
If you want a faster answer then try to show that you have made an effort yourself. A bit of code will encourage people to answer. Using words such as 'cuz', 'wanna' doesn't help either, a little effort in your grammar shows that you have taken then time in checking what you have said and shows that you, at the very least, care about what you have said. Firefox has build in spell check nowadays so there is no excuse
.
I can see that, like myself, your new so don't take this as a 'flame' but just a little advice to get quicker responses in the future.
Regards,
EDIT: Said all that and didn't upload the code. This example shows gravity and jumping, hit space to jump:
sync on
sync rate 60
Global Xpos
Global Ypos
Global VelocityY
Global AccY
VelocityY=0
AccY=0
Xpos=100
Ypos= 100
do
cls
`Spacekey Decreases the Velocity
if spacekey() then velocityY=-10:accy=1
`Sets Ypos + VelocityY as Jump height(-20,-19,-18,-17)
VelocityY=VelocityY+AccY
Ypos=Ypos+VelocityY
`Resets Velocity when reaches +10 to 0
IF VelocityY>10 then VelocityY=0:AccY=0
`Stops the Circle from dropping below 300px
If Ypos < 300 then Gravity = Gravity - 1
if Ypos > 300 then Ypos = 300: Gravity = 0
`Sets Gravity to Ypos
Ypos =Ypos -Gravity
`Display Circle affected by gravity
Circle Xpos,Ypos,10
sync
loop
http://dsarchy.deviantart.com/