Mixing and mastering are two very different parts of the recording process that confuse a lot of people. If you're recording an album that you are serious about and plan to take it somewhere, mixing and mastering is a necessity.
Once the recording phase is complete, the mixing phase begins. Mixing involves leveling, EQing, compressing, adding effects, editing/repairing audio and/or MIDI. Think of mixing as putting the pieces together to complete what has been recorded raw. Any finishing touches should be applied in this phase (i.e. adjust vocals, guitar, bass, drums etc). You should feel like the song is complete after the mixing process is complete. If you plan to get a track mixed, you need to export all the individual tracks (all the same length) and send it to a mixing engineer. The tracks should be in an uncompressed format (WAV or AIFF).
Mastering is polishing the mixed track (stereo mixdown). The first part of mastering that most people think of is the loudness. Loudness is important but is not the only thing that happens in the mastering phase. The average listener can listen to an unmastered and mastered version of a song and think, "it's louder". But in order to get the loudness to the industry standard (ready for radio, digital release or cd release), it needs to go through many steps (compression, limiting, EQ, normalization, reverb etc.). If you plan to get a track mastered, you need to export the mixed song to an uncompressed (WAV or AIFF) stereo file and send it to a mastering engineer.
Audio mixing is the process by which multiple sounds are combined into one or more channels. In the process, the source signals' level, frequency content, dynamics, and panoramic position are manipulated and effects such as reverb may be added. This practical, aesthetic, or otherwise creative treatment is done in order to produce a mix that is more appealing to listeners.
Mastering, a form of audio post-production, is the process of preparing and transferring recorded audio from a source containing the final mix to a data storage device (the master); the source from which all copies will be produced (via methods such as pressing, duplication or replication). Recently digital masters have become usual although analog masters, such as audio tapes, are still being used by the manufacturing industry, notably by a few engineers who have chosen to specialize in analog mastering.
The mixing and mastering process is actually very simple to understand. It all falls into place once you get the idea. The art of mixing and mastering requires years of experience and techniques but if you don't have a budget for it,you can get the job done with some dedication. A tip from us here at Production Trends: use different speaker sources to reference you mixes to get the most accurate mix possible. If you plan on purchasing software to learn it yourself, we recommend Pro Tools by Avid.