The epsilon (backward 3) is the vowel sound in end, head, bed, then, etc. Whereas the schwa, or upside-down e, is a generalized vowel made with a relaxed, barely opened mouth.
The best ways to figure out the exact sound of an IPA vowel is checking out the vowel chart, which is arranged depending on the articulation in the mouth. This version also has audio for every symbol, which is an even easier way to grasp the exact pronunciation.
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