Collections allows us to store a group of elements of type both “Homogeneous and Heterogeneous”.
(i.e. Collections allows us to store Similar Type of Elements and Dissimilar Type of Elements)
Collections purely supports Dynamic Memory Allocation. Hence the Collection size Can Grow / Shrink at a runtime. Collection avoids the Memory Wastage. i.e. We can utilize the memory very efficiently.
Collections allows us to store the elements of type “Primitive Type, SObject Type, Collection Type, Apex Type and User Defined Type”. Collection Elements will get resides inside the “Heap Memory”.
Collection provides a set of readymade methods to be get used to manage the elements inside the collection.
We have the below 3 Collection classes.