Capo's are great for things like changing key and eliminating difficult to play chords, for example, but they are also useful for other reasons.

For example, they can help youngsters with guitars which are slightly larger than suits their age and which they are expected to grow into. Placing a capo on, say, the third of fifth fret, has the effect of shortening the fretboard and consequently the spacing of the frets, thus making the instrument much easier to play for small hands and fingers.

Also, it is quite common for inexpensive guitars not to play in tune, particularly at the first fret. If that is the case for you, and you can't afford to have a luthier/guitar maintenance person resolve the problem, just try placing a capo at the first fret and it is likely your guitar will play more in tune. Obviously this raises all your open strings by a semitone, so if you want to keep the original tuning, for singing certain songs etc, you can retune your guitar a semitone down (Eb, Ab, Db, Gb, ...

I often hear people say they find it hard to stretch their fingers to play certain chords when they first start to play because they have small hands. Well, for those folk this seemingly obvious recommendation will be a great help and will also make early-learning life much easier for budding young guitar players who are often bought guitars which are too large for their age. 

First, if you don't have one already buy a capo. You can use any straight full-width capo or an adjustable 6-string capo such as a Flexi-Capo or Spider Capo if you already have one. Now, because the gaps between frets become smaller as they progress towards the guitar body you can take advantage of that situation by positioning the capo on any fret which makes fingering chords easier for you - if you play a lot of open chords, as beginners often do, you can even start with your capo set on the 7th or 8th fret. You will probably be amazed at how chords suddenly become so much easier to play. 

As you make progress ...