Not a dumb question at all. A haplogroup is a grouping of common patrilineal or matrilineal lines who share a common ancestor. The main haplogroups are divided by letter, and smaller sub-divisions by letter and number. For example H isa very large group, H1 is a subgroup of H, H1a is a subgroup of H1, and so on. The further you narrow it down the closer in years the common ancestor is.
There are small parts of our DNA that do not change much over time. Geneticists have used these parts to identify population groupings, where they live, and their movement through human history. Certain haplogroups occur with greater frequency in certain areas which is what leads to them be categorized as African, European, Asian, Native American etc.
Males have a paternal and a maternal haplogroup. Their paternal haplogroup is inherited along a direct paternal line - your father's father's father's, etc.. The maternal haplogroup is inherited from your direct maternal line. Females only have a maternal haplogroup.
Here is a mapping of maternal haplogroups: http://www.worldfamilies.net/files/image/migration_map_wfn(1).gif
You can see from this map what part of the world the groups are associated with. If you get into the details of the haplogroups it will show how the groups branch out from one another. On a long enough timeline everyone's ancestry goes back to Africa (more than 50,000 years ago). But these haplogroups identify ancestry in more recent times (within the last 50,000 years)
For example my mother is haplogroup H. This is the biggest group for Europeans. It is estimated that the common ancestor of this group is a woman who lived in the Caucasus between 33,000 and 26,000 years ago. Depending on the test you take you can get more detail.
My mother did an mtDNA test that further narrowed her haplogroup to H1as. Certain lineages of H1 are thought to have been introduced by hunter-gather women up to 18,000 years ago. H1a is thought to be a common ancestor 2000 years ago and is tied to many Europeans of Romany (Gypsy) ancestry. This would suggest that if you followed my mother's direct maternal line back past genealogical times the most likely ancestry would be a Romany Hungarian. My mother's European ancestry is heavily German - so this makes sense.
Keep in mind that the understanding of these groups changes over time as people learn more.