what is the difference between bezier and pen tool

They are actually very similar, and I have previously suggested that they should merge these two into one, to avoid the confusion.

The preview for the Pen tool that Shakti mentions can be turned off in Property Bar (which makes them even more similar).

Not sure how Ariel means but there is indeed a difference in how you create a straight line directly after a curve segment.
Pen tool: Press Alt and then click on last node.
Bézier tool: Double click last node.

To create a Cusp node, press c after creating a node, preferably while dragging the node handle.
With the Pen you you can also click on the last node while pressing the Alt key, the same way as when creating a line (mentioned above).

I personally prefer the Pen, partly because of the preview but also because of a "hidden" feature.
While drawing with the Pen tool, press Ctrl and click any node on the curve to enter a "node editing mode".
This allows you to move and change nodes, and when you are ready simply click outside the curve to return to the Pen tool.