A camera can only hold as much data as the microSD card can hold unless it has an internal memory of some kind, so this all depends on the size of your SD card. You may find that some cameras will only accept a certain limit, such as 32 GB. But, no matter, even 1 or 2 GB SD cards will hold a ton of photos. However, it does depend on the number of megapixels on the camera. The more you have, the larger the file size will be for each photo.
For this example, let’s assume that you have a camera with 10 megapixels (which would equate to around a 3 MB file size for a photo). With a 4GB SD card, you could hold around 1,000 photos. Increase this to 32 or 64 GB and then you are talking about holding 9,000 and 18,000 photos. This is just for photos as videos, especially those rendered in 1080p, will be massively increased in size.