with Katakana (Angular characters), you will be sounding out foreign words. You will get an Engrish like sounding word.
stuff like "enboropu" will be "envelope"
Knife would be like "naifu", etc.
With Hiragana (curvy stuff), you will get words... that will then need to be looked up and translated in a Japanese dictionary. It's a bit trickier!
You'll find Katakana is enough to navigate menus and do the basics.
There are some other things you will encounter... a dash means extend the previous letters sound, and then theres somme special things that will usually appear on a good chart.