CAM is the software tool that helps you create toolpaths over your model. While simple 2d outlines are quite readily offset for tool radius and then converted to dxf and then to gcode with some convertor type applications, this covers only the simplest machining applications. Such convertors may be quite deficient in supplying Z axis control codes to permit your tool to safely enter and/or clear the work at the proper moment.
Now, if you do much more toolpath drawing manually, you can improve the entry into the part with ramps, helical entry and so on. Good CAM will give you these options and add them to your gcode automatically.
While it can be quite entertaining and interesting to draw your toolpaths manually for a while, this can get to be a bothersome chore. Tweaking the toolpath to bring the part into tolerance basically means "start over" with your toolpathing. That gets irritating after you get to the point of wanting to see some output from your machine.
Beware of cheap cam software that does not create and simulate toolpaths from a solid or surface model. Those programs are simply outdated in today's world, kind of like the DOS operating system. If you are using something like Alibre, chances are you are doing more than sketching a few lines on the screen, but everyone has different requirements to achieve what they want. If you can better describe what you intend to machine, then better advice can be given for what to look for, for cam software.