Sound is created by vibrations. How fast those vibrations are is called "frequency." There is a range of vibrations that the human ear is sensitive to. The slower, bigger vibrations in this range are called "bass." The faster, smaller vibrations are called "treble." Everything else is called "midrange." Many sounds can be a mixture of both kinds of vibrations, and (to add to the confusion) bass notes can generate a kind of "ghost tone" over top of them in the treble range, called "overtones".
Usually bass sounds are conceptualized spatially as "low," and treble sounds as "high." This can cause confusion with (for example) a guitar, where the (larger, thicker) bass strings are at the top, and the treble strings at the bottom. A good way to think of bass versus treble is that bass is characteristic of the voice of (some) adult males, with treble being more like the typical voice of a little girl.
In an audio system, bass sounds are created by large speakers called woofers and sub-woofers, and can vibrate your entire body if they are loud enough. Treble sounds are created by tiny speakers called tweeters, and can be very ear-piercing. Another difference is that treble sounds are experienced as coming from a specific direction, while bass is largely non-directional (because it washes over your whole body). If you have earphones, and you hold them at a distance from your ear, you will only hear the treble. If you press them into your ear, it will tend to make the bass sound louder.