The other answers are pretty good already. Here's a very quick and dirty description of a MIDI file format:
A MIDI file may contain up to 65,536 tracks (usually these tracks are intended to play simultaneously). Each track is just a sequence of events. Each event occurs at a specific time (specified as the number of "ticks" since the beginning of the track), and describes a message that gets sent (usually to either a hardware or software synthesizer). There are many types of events, but they usually belong to one of two types: Channel Events, and Meta Events (I'm ignoring a third type called System Exclusive events).
Meta Events don't necessarily contain musical information, but rather metadata, such as a track name, instrument name, or lyrics. They also can contain "gloabl" information that affects the entire playback, such as tempo, time signature, and key-signature are also treated as meta events. In your sample data, the MIDI_port and Title_t (which is the track title) are meta events.
Channel Events are where most of the musical action occurs. These include things like playing notes (Note On and Note Off events), depressing/releasing the sustain pedal, changing the instrument (or "patch"), introducing pitch bends, changing the volume or pan settings, changing effects like reverb or chorus, tweaking the synthesizer parameters like attack and sustain, etc...
The important thing to keep in mind about channel events is that they are all tagged with a "channel" number (from 1 to 16 -- or technically 0 to 15, depending on the software) and they will only affect other events that are on the same channel as they are on. So, for example, a note that starts with a Note On event on, say, channel 7 can only be stopped by a Note Off event on channel 7. A "sustain pedal" event on channel 3 will only sustain notes that are played on channel 3. Changing the instrument on channel 2 to a Xylophone will cause all notes on channel 2 to be played on a Xylophone, etc...
For Note On events, you have to specify what channel the event occurs on, but also the pitch (note number in semitones, where 60 is middle C) and how hard the key is struck ("velocity", from 0-127, which usually determines the loudness). Once the note begins, it will continue playing until a Note Off event is received for the same pitch and channel. Or alternatively (as in your case), you can send another Note On event with a velocity of 0. So in your case:
2, 3072, Note_on_c, 1, 26, 96
This says that track 2 contains the following event: At 3072 ticks after the beginning of the song, begin playing note 26 (the D just shy of 3 octaves below middle C) on channel 1, with a "velocity" of 96 (out of 127, that's probably about a mezzo-forte). This note will stop playing later, when the following event is received (because it has the same channel & note, but has a velocity of 0). It occurs 148 ticks later.
2, 3220, Note_on_c, 1, 26, 0