In Southern California we have two high tides and two low tides each day. Generally one of the high tides higher than the other (the "high" high tide) and one of the low tides is lower. They are caused by the gravity pull between the earth, moon, and sun. The time of the tides change by about 50 minutes each day as the moon migrates through its monthly cycle.
If you live somewhere else, search for closest coast to you at this website. The height of the tides are compared to an average local low, low tide.
So, a low tide of -0.1 ft is below average. A
high tide of 5 ft is pretty high in this area.
Some places (like Alaska) may have high tides of
more than 20
This site about tides
has a pretty good description and pictures
of how tides work. When you take physics some
day, you will learn an even more detailed explanation.