So if you're shooting photos with a digital camera chances are you're going to need a memory card.
There are a lot of different kinds of memory cards out there but the two most popular formats are something called CF which stands for Contact Flash, looks something like this. Most DSLR's and professional level gear use CF cards however there are a whole lot of cameras that also use something called an SD card which looks something like this.
Most pro-sumers to high end DSLR's will even use these which are very, very pro-level stuff will use contact flash.
Now it's important to make sure you have enough memory on your memory cards for all the photos you're going to shoot, goes without saying. Most photographers will carry maybe not this many memory cards around but have a couple as back up.
Memory cards have a tendency to sometimes get what's called corrupted which basically means the filing system and the naming system get out of whack with each other and you can't use the card, really good reason to have a second one on you.
I personally prefer to use eight gig memory cards. They come in a variety of sizes everything from a one gig all the way up to 64-gig, 128-gig. If you're thinking of doing video with DSLR or your point and shoot, more memory is always better because video files you have to remember are inevitably be much larger than still files.
So one of the advantages of CF cards is that they're just thicker and more reliable than SD cards which are a little bit flimsy, kind of easy to lose which is another really great reason why professionals prefer CF.
A good thing to keep in mind is if you're using CF cards you're going to need a CF card reader. They generally go for about 10 bucks, they're not super expensive whereas most computers these days have an SD card reader built in so you're obviously not going to need to go out and purchase that.
Memory cards have different speeds correlating to how fast they can transfer data. This one in particular is 16 mega bites a second. If you're doing video with your camera you're going to want a faster transfer rate just because it's going to make your life a lot easier with all the data you’re moving.
However, if you're just using stills, it's really not going to make a whole lot of a difference. An important thing to remember and I'm going to just toss this in as a PSA, avoid at all cost buying memory cards on eBay because eBay is rampant with sellers selling knock off cards and it's really a good way to get a bad card and loose a lot of photos and be really upset. Don't do it.