Not dumb at all, the text and font properties are very easy to get mixed up in the beginning. From a non-technical, layman’s point of view, why not text-size? It is the size of the text we are trying to change after all. With better knowledge about fonts, some of the properties may make a little more sense.
Some more info, for you, or anyone else reading this, feel free to ignore:
Turns out, practically speaking, there are pretty much just 4 variations of each of the two properties you need to remember, in time they will become second nature to you.
List of properties with random, although common, values.
Side note/tangent: A big help is the browsers developer tools, pick an element by right clicking and inspecting it. Under styles start to write the name of the property, say text, and a dropdown list of all the text properties shows up, once you have selected the property the same happens for the property values. If you are ever in doubt about the names of properties (or property values) it can be a good place to look and is very handy.
Because of the auto-completion and immediate visual feedback, it is my number one recommended way to both learn and work with CSS. Combined with DOM inspecting and the visual highlighting of element boxes with their margin and padding, it really does make CSS much more tangible and also provides visual learning.