@Dynasty Warrior
Let's say you want both cross chop and ice punch on electivire. He's in humanshape egg group. There's no pokemon in that group who learns both naturally. So, you need to find a pokemon who can learn Cross Chop/Ice Punch by level up and can get the other move by breeding. In case of Electivire, this is machop. Then, you search for pokemon who can learn the second move naturally. In case of electivire, this is Hitmonchan. So, you level up machop and hitmonchan so machop knows cross chop and hitmonchan knows ice punch, breed so you get machop with ice punch and cross chop, then breed it again with electabuzz/electivire, and get Elekid knowing both ice punch and cross chop.