A press cloth is a piece of fabric used when applying more heat than you usually would when ironing a fabric. They provide a barrier to protect your fabric from direct contact with a hot iron.
Hams and sleeve rolls are very firmly packed pillow type curved objects with two different types of fabric surfaces.
Presser bars are sticks of wood with a flattened end. They work well to hand press small seams on craft objects or when an area is totally impossible to reach with an iron.
Small ironing boards are miniature versions of the ironing board everyone has in their closet.
Use: A press cloth is essential to prevent scorching your fabric when you are applying more heat than you would if you were just ironing out wrinkles. They are available in different weights. A see-through press cloth allows you to see the pressing task through the press cloth. If you do not have one, a piece of muslin will do but it is an item worth adding to your sewing tools.
Hams and sleeve rolls are wonderful for pressing curves and seams that are in a tube area without creasing another area of the garment. Similar results can be achieved with a tightly rolled towel. It is worth saving up for a pressing ham and sleeve roll if you will be sewing clothing, baby clothes or doll clothes.
A small ironing board can achieve pressing the inner seam of some tubes. Because it has a stand, it is not as flexible to use as a sleeve roll.
Care & Maintenance: Always read the information that comes with any tool to prolong the life of the tool.
Expense: I have found pressing tools in dollar stores. I have also found ironing systems for hundreds of dollars. They are items that can be added to your sewing tools one at a time, choosing the one you would use the most first.