Update README

Author: trinhanhngoc

README.md

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 # pydevd-odoo
-PyDev.Debugger plugin for Odoo
+
+[PyDev.Debugger](https://github.com/fabioz/PyDev.Debugger) is the Python debugger used
+in PyDev, PyCharm, VSCode. This plugin makes the debugger better for Odoo
+development.
+
+## Odoo Recordset
+[Recordsets](https://www.odoo.com/documentation/13.0/reference/orm.html#recordsets) is a fundamental concept in Odoo.
+A recordset is an ordered collection of records of the same model. Trying to read a field
+on multiple ids recordset will raise an error. Because PyDev.Debugger recognizes a recordset as a
+non-collection object so the error will be raise when evaluating its attributes. This plugin helps
+PyDev.Debugger correctly evaluate an multiple ids recordset.