Docs: Add glossary (#19148)

* Create glossary.md

* Update glossary.md

Added definition for panel

* Update glossary.md

* Update glossary.md

* Update glossary.md

Fixed closing table tag

docs/sources/guides/glossary.md

++++
+title = "Glossary"
+description = "Grafana glossary"
+keywords = ["grafana", "intro", "glossary", "dictionary"]
+type = "docs"
+[menu.docs]
+name = "Glossary"
+identifier = "glossary"
+parent = "guides"
+weight = 4
++++
+
+# Glossary
+
+This topic lists words and abbreviations that commonly used in the Grafana documentation and community.
+
+<table>
+  <tr>
+    <td style = "vertical-align: top;">Dashboard</td>
+    <td>A set of one or more panels, organized and arranged into one or more rows, that provide an at-a-glance view of related information.</td>
+  </tr>
+  <tr>
+    <td style = "vertical-align: top;">Data source</td>
+    <td>A file, database, or service providing the data. Grafana supports a several data sources by default, and can be extended to support additional ones through plugins.</td>
+  </tr>
+    <tr>
+    <td style = "vertical-align: top;">Graph</td>
+    <td>A commonly-used visualization that displays data as points, lines, or bars.</td>
+  </tr>
+    <tr>
+    <td style = "vertical-align: top;">Panel</td>
+    <td>Basic building block in Grafana, composed by a query and a visualization. Can be moved and resized within a dashboard.</td>
+  </tr>
+  <tr>
+    <td style = "vertical-align: top;">Plugin</td>
+    <td>An extension of Grafana that allows users to provide additional functionality to enhance their experience. The types of plugins currently supported are:
+    <ul>
+      <li><b>App plugin:</b> Extends Grafana with a customized experience. It includes a set of panel and data source plugins, as well as custom pages.</li>
+      <li><b>Data source plugin:</b> Extends Grafana with supports additional data sources in Grafana.</li>
+      <li><b>Panel plugin:</b> Extends Grafana with additional visualization options.</li>
+    </ul>
+    </td>
+  </tr>
+    <tr>
+    <td style = "vertical-align: top;">Query</td>
+    <td>Used to request data from a data source. The structure and format of the query depend on the specific data source.</td>
+  </tr>
+    <tr>
+    <td style = "vertical-align: top;">Time series</td>
+    <td>A series of measurements, ordered by time. Time series are stored in data sources and returned as the result of a query.</td>
+  </tr>
+  <tr>
+    <td style = "vertical-align: top;">Visualization</td>
+    <td>A graphical representation of query results.</td>
+  </tr>
+</table>