There are many different types of fabrics to use for your cross stitch project, all of which are measured in thread counts. For example, a 14 count fabric means that there are 14 threads in a single inch. The higher the thread count the smaller the squares and the less the x's are visible.
Aida is most common fabric and my recommendation for anyone starting their first project. Aida is 100% cotton and is easily found in 11, 14, 16 and 18 counts with 14 being the most popular size and the size that all my patterns are based on. With a little searching you can find aida in even more sizes such a 7 or 22. It has a stiff feel to the hand and can be easy to use for in-hand stitching or with little tension. I recommend choosing aida for any beginning cross stitchers!
Evenweave is a type of weave with a one over, one under weave structure. You can find different types of evenweave fabrics such as Jobelan, Lugana, Belfast or Monaco fabric which vary in fiber content. Evenweave is usually much softer to the hand and needs more tension for stitching. Evenweaves are typically found in larger counts such as 25, 28 or 32 (as well as many sizes in beween) and can be stitched over 2 threads to give the same final sizing as 14 or 16 count aidas.
If you’re still not sure which one to pick for your project, consider if your pattern has fractional stitches, detail back stitching, or french knots. If the answer is yes, evenweave can be easier to stitch with.