For the present you need only concern yourself with understanding quarter and eighth notes. Progress will be best accomplished by following the above counting instructions and then applying them to the rhythms in the various sections of this page. If not, practise these rhythms playing along with tape or radio. It's a good enough substitute and helps you to keep in time. Not being able to keep up with something that is just too fast can be frustrating.
Most music is mathematically balanced and logical.
Accent - An 'arrow' placed above a note means that the note is accented. Accented notes are, essentially, played louder than other notes in the phrase, which do not have the accent symbol placed above them. Accents in percussive phrases really 'make' the rhythms and it is important to develop your ability to play the phrases with the accented notes standing out distinctly against un-accented notes. The caixa pattern for Samba Batucada is a good example with which to practice playing accented notes, as it features accents played by both hands. One two three four.