Look at this picture. Gutter on a house screw into the fascia board. Fascia is the covering of that board(if any at all. The most common fascia is simply a painted aluminum pre-bent sheet. The protects the wood and also allows a maintenance free covering. There are also vinyl coated aluminium coil stocks in many matching colors for your vinyl siding. It really is quite simple and just nails in. Saves you from painting and adds some great color.
In recent years some very nice fascia options have entered the market which we will talk about now.
Vinyl Coated Fascia Panels – a rich option that stands out
Many manufacturers are offering aluminium coil stock that in vinyl coated with a woodgrain emboss. This same product can be bent to use as a fascia board. Otherwise some even make actually prebent fascia panels like this. If you are having your doors and windows trimmed out this is a great matching option to go on your fascia as well. Combo up with the matching soffit panels from your siding supplier and you are good to go. Vinyl coated aluminium has a good advantage over painted aliminum. For one it tougher and does not scratch easily. Additionally, it is much more fade resistant than regular painted aluminum. Lastly, there is the option of a wood-grain or textured embossing which you will really like.
How about skipping the fascia all together and just getting a colored (or white) composite fascia board. These are man made boards that never rot, warp, require finishing or painting. The color is all the way through and is available either flat or wood grain. Many people know of this product through composite decking and indeed it is basically the same stuff. There are many manufacturers so the sky is the limit. Get ready to write a big check though. Changing your whole house to this is 5-8x more expensive that using an aluminium or vinyl coated aluminum fascia cover. If your a building a new home though this is a great choice.