The Latches chart shows statistics on Latch requests. A Latch is like a mini-lock that is used internally by SQL Server to serialize access to certain resources. Latches do not participate in transactions and are typically held for a very short duration.
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The Latches chart shows the following:

Latch Waits/sec

How many waits for latches occurred per second.

Total Wait Time (ms)

The total amount of time that latch requests spent waiting during the last second, measured in milliseconds.