Update verbiage (#788)

Author: b-nagaj

docs/concepts.md

@@ -23,7 +23,7 @@ each other so that it does not matter which one of your 1000 things of Part you
 A part entity has many fields, which can be used to describe it better. Most of the fields are optional:
 
 * **Name** (Required): The name of the part or how you want to call it. This could be a manufacturer-provided name, or a
-  name you thought of yourself. The name have to be unique in a single category.
+  name you thought of yourself. Each name needs to be unique and must exist in a single category.
 * **Description**: A short (single-line) description of what this part is/does. For longer information, you should use
   the comment field or the specifications
 * **Category** (Required): The category (see there) to which this part belongs to.
@@ -239,4 +239,4 @@ replaced with data for the actual thing.
 
 You do not have to define a label profile to generate labels (you can just set the settings on the fly in the label
 dialog), however, if you want to generate many labels, it is recommended to save the settings as a label profile, to save
-it for later usage. This ensures that all generated labels look the same.
+it for later usage. This ensures that all generated labels look the same.