Is a rhombus a rectangle

No.

A rhombus is more like a diamond than a rectangle. A rectangle is straight while a rhombus is more slant-y. Both have parallel lines.
not necessarily. but all rectangles are rhombuses. for a figure to be a rectangle, it must to two sets of parallel sides and all of its angles must be right angles. rhombuses have to sets of parallel sides, but they don't necessarily have all right angles.

hope this makes sense