Improved dev docs

help/en/developer/core/engine.rst

@@ -2,6 +2,35 @@ core.engine
 ===========
 
 .. automodule:: core.engine
+    
+    .. autoclass:: Match
+    
+    .. autoclass:: Group
+        :members:
+    
+    .. autofunction:: build_word_dict
+    .. autofunction:: compare
+    .. autofunction:: compare_fields
+    .. autofunction:: getmatches
+    .. autofunction:: getmatches_by_contents
+    .. autofunction:: get_groups
+    .. autofunction:: merge_similar_words
+    .. autofunction:: reduce_common_words
+    
+.. _fields:
 
-.. autoclass:: core.engine.Group
-    :members:
+Fields
+------
+
+Fields are groups of words which each represent a significant part of the whole name. This concept
+is sifnificant in music file names, where we often have names like "My Artist - a very long title
+with many many words".
+
+This title has 10 words. If you run as scan with a bit of tolerance, let's say 90%, you'll be able
+to find a dupe that has only one "many" in the song title. However, you would also get false
+duplicates from a title like "My Giraffe - a very long title with many many words", which is of
+course a very different song and it doesn't make sense to match them.
+
+When matching by fields, each field (separated by "-") is considered as a separate string to match
+independently. After all fields are matched, the lowest result is kept. In the "Giraffe" example we
+gave, the result would be 50% instead of 90% in normal mode.

help/en/developer/index.rst

@@ -23,6 +23,8 @@ codebase. For example, when performing "Remove Selected From Results",
 ``base.app.DupeGuru.remove_duplicates()`` on the PyQt side, are respectively called to perform the
 thing. All of this is quite ugly, I know (see the "Refactoring" section below).
 
+.. _jobs:
+
 Jobs
 ----