Update README.md with explanation of tags

README.md

@@ -6,6 +6,16 @@
 Latest DockerHub Images: https://hub.docker.com/orgs/coffeateam/repositories
 
 
+# Coffea image tags
+
+
+* `dev-` tags represent the status of `dev` branch
+
+* `head-` tags represent the status of `main` branch
+
+* `202x.x.x-` and `0.7.x.-`, as well `latest`  represent relevant tags in [this repository](https://github.com/CoffeaTeam/af-images/tags)
+
+
 # Coffea 2024 images
 
 * Dockerfiles and conda environment files are available in `coffea-dask` directory
@@ -28,6 +38,3 @@ Latest DockerHub Images: https://hub.docker.com/orgs/coffeateam/repositories
 | coffea-base-alma9     | Alma9 Dask Coffea 0.7.x image with latest XrootD and CA certicates            | ![Docker Image Version](https://img.shields.io/docker/v/coffeateam/coffea-base-almalinux9) |
 
 
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