An alert is the outcome of an alerting rule in Prometheus that is actively firing. Alerts are sent from Prometheus to the Alertmanager.
The Alertmanager takes in alerts, aggregates them into groups, de-duplicates, applies silences, throttles, and then sends out notifications to email, Pagerduty, Slack etc.
A bridge is a component that takes samples from a client library and exposes them to a non-Prometheus monitoring system. For example the Python client can export metrics to Graphite.
A client library is a library in some language (e.g. Go, Java, Python, Ruby) that makes it easy to directly instrument your code, write custom collectors to pull metrics from other systems and expose the metrics to Prometheus.
A collector is a part of an exporter that represents a set of metrics. It may be a single metric as part of direct instrumentation, or many metrics if it is pulling metrics from another system.
Direct instrumentation is when instrumentation is added inline as part the source code of a program.
An exporter is a binary that exposes Prometheus metrics, commonly by converting metrics that are exposed in a non-Prometheus format into a format Prometheus supports.
A notification represents a group or one of more alerts, and is sent by the Alertmanager to email, Pagerduty, Slack etc.
Promdash is a Ruby-on-Rails dashboard builder for Prometheus. It is similar at a high-level to Grafana, but is specific to Prometheus.
Prometheus usually refers to the core binary of the Prometheus system. It may also refer to the Prometheus monitoring system as a whole.
PromQL is the Prometheus Query Language. It allows for a wide range of operations including aggregation, slicing and dicing, prediction and joins.
The Pushgateway persists the most recent push of metrics from batch jobs. This allows Prometheus to scrape their metrics after they have terminated.
A silence in the Alertmanager prevents alerts with labels matching the silence from being included in notifications.
One application, server or endpoint that Prometheus is scraping.