Breath marks (related to caesurae) often appear in scores for woodwind instruments where it is acceptable to take a breath of air. They are placed in a passage where the phrasing will not be disrupted.
A breath mark will necessarily mean that the note preceding it will have to be played slightly shorter than denoted (much is the same way a grace note will steal some time from the note preceding it).
Breath marks are usually engraved with a comma like symbol placed above the staff.
Alternatively a tick mark like symbol (or even an up bow symbol) is sometimes used instead.
When a breath mark is optional (for a player with a greater lung capacity), the breath mark can be placed in parentheses.
This excerpt from a piece of music (for descant and treble recorders) has be written with both the tick type and the comma type symbols (for breath marks?):
Are these different symbols supposed to represent different types of breaths (perhaps one is longer than the other)?
Is the the comma representing something else? (perhaps a breath mark with a fermata/pause?)
Is something else going on?