There are many kinds of artist easels on the market. Some specifically for indoor painting, and some for outdoor painting. The most important thing to keep in mind, is to choose one that is sturdy, how you are going to use it; and of course, the cost. Some can be quite expensive.
The Studio Easel
There are basically two different styles of artist easels that stand on the floor. There are some with three legs and some with four legs. I would say that the four legged easel to be the most sturdy. However, the three legged easel might do better on an uneven floor surface.
There is also several models of table easels. One of these could be your choice if you prefer to sit to paint.
If you intend to paint outdoors, then you are definitely going to need some kind of painting support. There are several artist easels available for outdoor painting. Most of these can be adjusted so that you can paint from a standing or a sitting position. The Jullian French box easel is an easel and paintbox combination. It will hold most of your painting supplies. It also includes a wood palette. I use the sketching or, (field easel) and carry a fishing tackle box for my paints and supplies.
I also use a small pochade box with thumb hole. It can carry and hold one 6×8 canvas panel. It can also accommodate a 10×8 panel, (for painting only). I have a 10×8 panel carrier that can pack extra 6×8 and 10×8 panels. More on that later. The pochade box being quite small is useful for packing into remote areas. In inclement weather, you will find it to be convenient to set up and paint in your vehicle.
There is another; the gorilla box easel, which is slightly larger than the pochade easel. Most can be mounted on a tripod.