Two main types of freeway interchanges are the diamond interchange and the cloverleaf interchange.
A diamond interchange is where a freeway and a road meet. Traffic from the freeway can keep going or veer (turn a little bit) onto a road on an offramp. This meets a road at a stoplight. Traffic can also go from the road to the freeway by going on an onramp. It is called that because it looks like a diamond.
A cloverleaf interchange is where two freeways meet. There are still on- and offramps, but no stoplights and no right turns across traffic. To turn left, traffic goes in a 270° turn. It is called that because it looks like a four-leaf clover.