What is the difference between Dark Matter and Anti-Matter?

Antimatter is essentially the same thing as normal matter, except that certain charges have the opposite value. Amongst each other, antimatter particles can form the exact same structures as normal matter - a world made from antimatter would look no different than ours. Only when matter and antimatter come into contact with each other, opposite particles annihilate each other, leaving only radiation. Antimatter can be and is created in nature and particle accelerators.
Dark matter is a theoretical construct needed to explain why galaxies move like there is a lot more matter (gravity) than we can see. There are various theories what dark matter might be made of; but so far, there isn't much data to work with. Whatever it is, it's invisible and generally doesn't interact with normal matter in the usual ways; we only assume it's there because of its gravitational effects on normal matter.

Dark Matter is REGULAR matter which cannot be otherwise located. It COULD be just zillions and jillions of tiny dust particles that we can't see.

ANTI-MATTER has an opposite electrical charge from Regular Matter.

You know what matter is; you're made of it, so's your house, your books, and the computer you're using.
Matter is made up of atoms, which for the most part are made of positively charged Protons and neutral Neutrons in the nucleus, surrounded by equally negatively charged electrons, orbiting the nucleus in particular regions.
Anti-matter is identical, however the charges differ - anti-protons in the nucleus are negatively charged, and positrons in the clouds surrounding the nucleus are positively charged. Anti-neutrons can also be present in the nucleus.
When matter and anti-matter contact, they are completely converted to energy. So, the atomic bombs that wiped out Hiroshima and Nagasaki - about as much mass as a pencil erasure was converted into energy in those explosions; about 1/2 that amount of anti-matter is needed to achieve the same effect.
So, Anti-matter is the exact opposite of ordinary matter... it would look the same, until matter touched it - if you met your antimatter self in space, shaking hands would end your trip really quick.

Dark matter... astronomers calculated how fast stars in galaxies should orbit their centers; when they finally were able to visually estimate the speed of these stars, they noticed they were moving *way* too fast for the amount of visible matter in these galaxies. So, there must be an unseen, unknown 'Dark' matter present to keep the galaxies from flying apart. Right now, we don't really know what dark matter is, but there are a couple of theories. "WIMPs" - weakly interactive massive particles is one possibility - they're massive, but would pass right through you without you ever noticing. 'MACHOs' is another form - Massive Halo Objects (I forget what the 'C' is...) that are a part of the galaxy's halo...
There are at least 10 experiments (most are set in deep mines) looking for these particles - but, so far... nothing's been found.

Anti Dark Matter

Hey, hey, hey, never ever apologize for being curious. It's an incredible trait to have. Everyone was a beginner at some point, and this is a really good question. Antimatter are antiparticles that have the same size as particles of ordinary matter but have opposite charge. For example, you have an electron, and a positron is the antiparticle. Positrons have the same mass as electrons but are positive in charge.
Dark matter is a little tricky but I'll try to keep it simple. It's hypothetical, and it doesn't interact with ordinary matter or light so you can't detect it with a telescope, but it makes up most of the matter in the universe. It was deduced from gravitational effects it had on visible matter.

Ant matter has the opposite charge as our matter. We use it in X-rays. No one knows what dark matter is, except it is really heavy...