Rubber stamps for business commonly show an address and corporate logo. They often have movable parts that allow the user to adjust the date or the wording of the stamp. They are used to date incoming mail, as well as to denote special handling for documents. In some countries it is common practice for formal documents such as contracts to be rubber-stamped over the signature as additional evidence of authenticity.
The main difference, without getting technical, is the quality of the impression and how long the stamp lasts between re-inkings.
Both are refillable and come in many colors. Self-inkers are made of water-based ink & pre-inked stamps are made of oil-based ink. Pre-Inked stamps are top quality and provide a solid, crisp impression while self-inkers offer a good impression at an economical price. Both of these styles are not recommended for glossy surfaces because they will smear.