Ollie includes about 900 glyphs, many of which are automagical substitutions to keep the text flowing smoothly, and to pseudo-randomly pick different glyphs to avoid repetition. With contextual alternates turned on (as they should be by default), most lowercase letters will alternate between at least two different forms. The powerful OpenType programming makes the font itself 'look back' (up to eight characters) on previously used letters; typing "banana" will give you three different a's and two different n's (the last a is a special 'end form' character).
The calt feature controls many other 'special effects' which all add together to give a smooth-flowing, hand-lettered look. These effects include start and end forms (and indeed, 'loner' forms) of many letters, which are automatically substituted in at beginnings or ends of words, or when the previous or next letter doesn't connect. Another special feature tests to see if there is room for the crossbar of t (or tt ligature) to extend further over the previous or next letter, or both, as is often the case. The last main effect of the calt feature is to substitute certain letters typed before any 'e' character, to make for a more natural connection (see the pe combination in 'Schizotype' in the first poster).
Ligatures should be on by default, for a much nicer looking tt combination, and a few others besides. The swash feature should be used sparingly (one glyph at a time, really) to apply a more extravagant look to g,j and y in the lower case, and quite a few of the upper case too.