deriv LSK ETT STT aSTA ALPH OLDHOMEPAGE NEWHOMEPAGE
The language described by /pANini, which was based in a spoken language variety of his time, is a variable-stress language, like Greek, English, Russian, Italian, Portuguese or Spanish.
That means that one of the vowels of (nearly) every word gets a high pitch, and the position of that high pitch may change meaning.
Fortunately for us students, this accent is no longer used in spoken Sanskrit, so we may safely ignore all /pANini rules that are only useful to regulate the accent — that's about third or half of the 4000 sUtras in the grammar.
Making a long story short — if you are only interested in spaking or reading /laukika, NVM the accent. The affixes /tRn and /tRc are actually just tR तृ.
Howver, the accents are used in Veda recitation, and they must be used in all mantras. So when you get dIkSA दीक्षा, pay attention.
You can hear some accented sanskrit sung here.
See also modern accent.