Well it's really unlikely that you don't know what hitpoints are, but we'll take the time to explain that to you anyway.
Your HP is basically the value of your health. Basically, the more you have, the more damage you can take. So higher HP means a greater chance of survival in combat. As you level, your HP will increase. Most likely not on every level at first as your stats affect your HP and SP. To learn more, check 'help stats'.
Note: When you receive damage, either in combat or by poison, your HP will will decrease. When it falls under 0, you die. For more information on the effects of dying, check 'help death'.
There are a few ways to regenerate HP. Naturally, by just patiently waiting for it to rise, by the use of curative spells, and by sleeping at an inn using the syntax 'rent'.
jp, sp, xp