Strictly, they're just words.
Telemetry is the act of gathering data remotely from your game:
Telemetry is an automated communications process by which measurements
are made and other data collected at remote or inaccessible points and
transmitted to receiving equipment for monitoring. The word is derived from
Greek roots: tele = remote, and metron = measure.
Analytics is the search for patterns in the data that you've gathered:
Analytics is the discovery and communication of meaningful patterns in
data. Especially valuable in areas rich with recorded information,
analytics relies on the simultaneous application of statistics,
computer programming and operations research to quantify performance.
Analytics often favors data visualization to communicate insight.
Software packages tend to provide one or the other (or some combination of both), but also tend to use the terminology interchangeably if it's for marketing or branding purposes. In other words, just because a product uses the term "analytics" in its name doesn't mean it only provides analysis, it may also provide a mechanism or hooks for gathering the source telemetry as well.
You probably wouldn't confuse anybody if you interchange the terms now and then, as they're broadly understood to be fairly related to eachother.