The rind of a fruit is the hard outer layer that you can't eat. Fruits like watermelon and oranges have rinds.
Sap is the thick, sticky fluid that is inside tree branches and stems. You can't see it until the plant is damaged in some way, like having a branch cut off or some kind of insect bores a hole into it.
Many kinds of sap are sweet and are eaten by birds and insects. People collect the sap from maple trees to make maple syrup. Latex is made from sap as well.
Spores are the way some bacteria, fungi, ferns and algae reproduce. One spore can grow into a whole new organism.
Spores are similar to seeds but they only need one parent not a male and a female parent like is needed to make seeds. Spores are also much smaller than seeds and do not have food reserves inside them.