Christina,
Spring tide is just a name for the "highest" of the high tides, when the combined gravitational effects of the sun and the moon are aligned. Most oceans have two high tides and two low tides daily but that is not always the case. Location, ocean floor topography, and flow constrictions can lead to only one high tide or one low tide daily.
The best way to think of it is that the sun has the greatest gravitational effect on the earth, followed by the sun. If the moon had a greater gravitational effect than the sun, then we would be circling around the moon as the moon circles around the sun!. Because water is very fluid (no pun intended) it can "shift" its relative position more quickly than the earth (which, when it comes to gravity from the sun and the moon is much more like a pliable plastic, like silly putty, It too responds to the combined effects of the sun and moon's gravities but just not in such an obvious way as water).
There are many sources for more detailed information on varying effects of gravity, just make sure the source you reference is real and not just someone's theory, the latter abounds on the internet.
