add fed vs multi search explanation

Author: guimachiavelli

config/sidebar-learn.json

@@ -261,6 +261,11 @@
         "source": "learn/multi_search/federated_search_guide.mdx",
         "label": "Federated search guide",
         "slug": "federated_search_guide"
+      },
+      {
+        "source": "learn/multi_search/multi_search_vs_federated_search.mdx",
+        "label": "Differences between multi-search and federated search",
+        "slug": "multi_search_vs_federated_search"
       }
     ]
   },

learn/multi_search/multi_search_vs_federated_search.mdx

@@ -0,0 +1,26 @@
+---
+title: Differences between multi-search and federated search — Meilisearch API reference
+description: 
+---
+
+# Differences between multi-search and federated search
+
+This article describes the different uses of federated search and multi-search.
+
+## What is multi-search?
+
+Multi-search, also called multi-index search, is a search operation that queries two or more indexes at the same time. Meilisearch returns a separated list results for each index. Use the `/multi-search` route to perform multi-searches.
+
+Multi-search favors discovery scenarios, where searches might have several valid results.
+
+## What is federated search?
+
+Federated search is a type of multi-index search. This operation also queries multiple indexes, but returns a single list with the most relevant results across all queried indexes. Use the `/multi-search` route and specify a non-null value for `federation` to perform a federated search.
+
+Federated search favors scenarios where users have a clear idea of what they need and expect a single best top result.
+
+## Use cases
+
+Because multi-search groups results by index, it is often useful when a document's index contains information relevant to your users. For example, a person searching for `shygirl` in a music streaming application is likely to appreciate seeing separate results for matching artists, albums, and individual tracks.
+
+Federated search is a better approach when the source of the information is not relevant to your users. For example, a person searching for a client's email in a CRM application is unlikely to care whether this email comes from chat logs, support tickets, or other data sources.