Faith
About
In a secular context, "faith" refers to the act of adhering to a particular type of belief in spite of
- the absence of substantial supporting evidence
- the existence of overwhelmingly contradictory evidence
In general, then, it means belief without regard to evidence.
By convention, the belief in question must be one that has a beneficial outcome, especially if the benefit isn't just to one's self but rather to the audience to whom one is speaking. An athlete might speak of having "faith" that the team would win the game or that s/he would play especially well (benefiting the team and its fans), but not that s/he would be the one to make the winning shot (benefiting only her/himself).
Common Usage
The word "faith" by itself is commonly used as a synonym for religious belief.
Implications
The idea of "faith" is usually seen or presented as a positive force, as it may enable individuals to act on their best instincts when a rational (but less complete) analysis would contradict those instincts; this usage is often conflated with having faith in the religious sense, implying that religious beliefs are somehow nobler or more beneficial than rational ones.