Pen tool

The Pen tool allows you to draw freehand. You can have straight or curvy segments from one point to another.

Under Edit>Preferences, make sure Pen Preview is checked.

As you draw

Start off by clicking to set your first point.
Click to add a straight line from the previous point.
Click & drag to create a curved line from the previous point.
Hold CTRL while you draw, lets you move the point. Let go and the point is anchored.
Click on the last point you added and you will undo the auto-curving for the next point you make.
Click on the first point you made to close the shape.

Editing

Using the Subselect tool

Select a point & move it
Select a point & delete it
Adjust the handles.

Using the Pen tool

Hover your mouse over a point:

click & drag to add curve to the point, or
click to make it straight (if it's a curved point), or
click to delete it (if it's a straight point)

Hover your mouse over a line:

click to add a straight point, or
click & drag to add a curved point

what the cursor can tell you