Central elements with four electron groups can have either zero, one or two lone pairs to give three possible molecular geometries. So if we take a look here, we have 4 electron groups and the way we can split this up is our center element could have 4 surrounding elements and no lone pairs. It could have three surrounding elements and 1 lone pair, or it could have two surrounding elements and 2 lone pairs.
If we take a look here, we have different examples of shapes that fit this criteria. Here we have methane, which is CH4. Here we have ammonia, which is NH3. And here we have water, H2O. Their visualizations show carbon in the center with its four hydrogens attached to it. Now here for nitrogen, we have our three surrounding elements and up top we'd have our lone pair. Remember, lone pairs have their own electron cloud which causes further repulsion. Water here would have two lone pairs on the oxygen, which causes further repulsion.
Now here, what are the names of the geometries? Well, if we have 4 surrounding elements and no lone pairs, it would be called tetrahedral. For the next one, it kind of looks like a pyramid with three legs, so that's why we call it trigonal pyramidal. And then finally, for water, we have two lone pairs on the central element and two surrounding groups. Here it kind of looks familiar to us. We saw shapes similar to this when we talked about two electron groups. We'd say that this looks bent or V-shaped or angular.
Now any one of these three terms could be used to identify this particular shape, so treat them all as the same. Just remember, when we have 4 electron groups, there are three possible molecular geometries that are possible.