added explanation what is solr

app.py

@@ -43,7 +43,7 @@ with gr.Blocks(title="Solr Normalization Demo") as demo:
     """
     # 🧹 Solr Normalization Pipeline Demo
 
-    This demo showcases the **Solr Normalization Pipeline**, which replicates the text preprocessing steps applied by Solr during indexing to help you understand how raw input is transformed before becoming searchable.
+    This demo showcases the **Solr Normalization Pipeline**, which replicates the text preprocessing steps applied by Solr <span title="Solr is the platform that provides search capabilities in Impresso. Several preprocessing steps must be undertaken to prepare data to be searchable in Solr. These steps are common in Natural Language Processing pipelines, as they help with normalising textual data by, for example, making the whole text lowercase. This makes possible non case-sensitive searches, where if you either write 'Dog' or 'dog', you can get the same results.">ℹ️</span> during indexing to help you understand how raw input is transformed before becoming searchable.
 
     The pipeline applies:
     - **Tokenization** (splitting text into searchable units)
@@ -63,6 +63,14 @@ with gr.Blocks(title="Solr Normalization Demo") as demo:
     """
 )
     
+    # Add Solr explanation accordion
+    with gr.Accordion("❓ What is Solr?", open=False) as solr_info:
+        gr.Markdown("""
+        **Solr** is the platform that provides search capabilities in Impresso. Several preprocessing steps must be undertaken to prepare data to be searchable in Solr. 
+        
+        These steps are common in Natural Language Processing pipelines, as they help with normalising textual data by, for example, making the whole text lowercase. This makes possible non case-sensitive searches, where if you either write 'Dog' or 'dog', you can get the same results.
+        """)
+    
     with gr.Row():
         with gr.Column():
             text_input = gr.Textbox(