I second Chas' recommendation of Hunter & Fuqua (third edition out now), second edition was one of the best photo books I ever read.
Re the two focal length indications, the first one is the mechanical/physical/optical indication. The second one is what is referred to as the 35 mm equivalent, so tell more about the type of image you get (wide angle, normal, tele). Let me explain with a quick detour through history.
Before digital, a SLR and many point and shoot film cameras were using so-called 35 mm film, producing a negative or slide with an area of 24x36 mm (there were some other formats as well, but let's skip that). Many people grew up with those 35 mm cameras, and some common rules (longest hand held time = 1/focal length) and type of lenses (normal = diagonal of image = 50 mm) are based on those 35 mm cameras and associated lenses.
Today, digital cameras come with many sensor sizes. A few high-end cameras are so-called full-frame: sensor size = 24 x 36 mm (same as old 35 mm film). There is APS-C (about 2/3 of that), and then there is half frame (12 x 18 mm). You seem to have a half-frame camera as the 35 mm equivalent is double your actual focal length. So the first lens is a moderate wide angle through normal to moderate tele/portrait lens. The second is a tele-zoom lens. The f-stop ranges are typical for entry level lenses, and as Chas has pointed out, lead to focusing problems in low light situations.
Re using them, this is a bit difficult to put in a nut-shell. I suggest, play around with them, and observe what is going on. Try to take the same flower image a the widest setting moving close, and at the longest setting moving further away. Observe how the image changes in look and feel. Do it with two flowers, put them side by side, or stagger them and observe, use different f-stops a the same focal length, and see how depth of field changes. Focus in different parts, using various depth of field settings, change lighting, etc. etc.
After playing around and making your own observations, re-read some of the books, and it should make more sense. My intro-photobooks are a tad out of date, focus quite a bit on dark-room (Stroebel et al., London & Upton), hence, I can't recommend anything current. If you really want to understand lenses, read Ray "Applied Photographic Optics". Possibly wait a couple of years, as it is a heavy hitter volume (with mathematical derivation, that can be skipped, though). It is among my top three photo books (the last one is Jack Dykinga "Large Format Nature Photography").
Eventually, you may find that you want more from your camera. Once you identify what the limiting factor is, then you can decide how to remedy it. If your large prints look blurry, you may need a larger sensor on the camera. If you cannot get close enough, you may need a macro lens. If you want more controlled lighting, some flashes may be indicated. If you want more control over perspective and placement of focal plane, look into large format. Be prepared to go through some iterations. I started out with SLR and one zoom lens (Yashica ~1982), then moved to Olympus OM4T/Ti SLR (also underwater in housing), Quick detour through Nikon F3HP SLR, a Pentax LX in an underwater housing, then to Contax RTS III SLR, added Arca classic compact 4x5 inch, now also have a full-frame Canon digiSLR. Lenses range from square fisheye to 300 mm tele-photo (f/2.8 vs yours at 5.6, so two f-stops faster), just a couple of flashes (macro and regular), and a bunch of various accessories. Needs/wants are different for each of us. Chas likes using an umbrella, I don't have one of those. Rather use a couple of 5-in-1 litediscs. We all have to figure out what works for each of us and where our priorities lie.
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