Rooibos, Fruit, Flower and Herbal Infusions are any "teas" that don't come from the Camellia sinensis plant. Sometimes they are referred to as tisanes and can include individual herbs such as peppermint or chamomile or blends based on apple pieces or raspberry leaf.
Apple pieces, hibiscus and raspberry leaf make really good bases for flavoured infusions as they take the flavour oils well. You will find that most fruit blends are based on apple or hibiscus with a small amount of added flavouring.
Rooibos is also a herbal infusion although it is sometimes referred to as "Red Tea". It can be used as a tea substitute and if brewed strong enough can taste similar to tea if milk is added. Rooibos makes a great blending base too and most flavoured blends that are made with a tea base can also be made with a rooibos base.
The main thing that sets infusions aside from tea is that most of them are naturally caffeine free.