The expansion slot is a very sophisticated approach to building a computer. Each slot connects its card to the data, control, and address buses and allows the card to interact in standard ways. Since all slots and cards are mutually compatable, many companies are making the cards, competition keeps the costs down. The constant pressure to beat out the competitor assures a constant flow of new and better expansion cards at reasonable prices. Cards and slots range from simple 8 bit to 16 bit and 32 bit cards.
Local bus are terms often used.
You should know what all these terms and factors mean. When installing a new card you will have to make sure that there isn't a conflict. Documentation with the cards don't always give complete instructions for avoiding conflict. Identify the range of features and limitiations of each kind of card. Define factors that affect your choice of each kind of card.