This time signature is called the three four time signature. It tells you there are three quarter note beats in each bar. This timing is frequently referred to as waltz feel e.g.:
The next example is in ^ time.
This time signature is called the twelve eight time signature. It tells you there are twelve eighth note beats in each bar.
Many slow songs are written in + time. A bar of eighth notes in twelve eight time sounds the same as a bar of triplets in four four time. Although there are twelve individual beats which can be counted, twelve eight time is usually still counted in four as demonstrated in the following example.
Here are two typical slow Blues bass lines written in + time. Once you get the feel of them, try creating some of your own.