There are four types of exchanges:
Simultaneous: you and another member exchange your homes at the same time.
Non-simultaneous: you exchange with another member but you travel at different times. If you don't know when you'll travel for the second leg, you can leave the dates blank and bank a future exchange.
Non-reciprocal: in this type of exchange, you stay in another member's home but they do not come to yours. In a non-reciprocal exchange, you have full use of the home. In People Like Us, you can host a non-reciprocal exchange just to make you feel good, or you can do it for a Globe, PLU's token system. When you earn a Globe, you can use it to travel to someone else's home.
Hospitality: also a non-reciprocal exchange in that only you travel to the other member's home and they don't come to yours, but in a hospitality stay, you only have partial use of the home and the other member will also be there. You can also use a Globe for a hospitality stay.