diff --git a/Database.md b/Database.md
index 2cba7d0..5691e0c 100644
--- a/Database.md
+++ b/Database.md
@@ -57,6 +57,8 @@ Assignment table represents exercise assignment in a group. It holds keys of the
 
 ## ReportedErrors
 
+All errors which were reported to api from backend are sent to administrator of system and also stored in this table.
+
 - _type_ -- textual description of error type
 - _recipients_ -- list of email addresses to which error was sent
 - _subject_ -- subject as it was sent in email
@@ -70,6 +72,8 @@ Assignment table represents exercise assignment in a group. It holds keys of the
 
 ## Role
 
+Roles serves for distinction of what user can do or cannot do. Thus every user has to have assigned some particular role from which decisions about access rights are made.
+
 - _id_ -- role textual identification
 - _parentRole_ -- reference to parent role
 - _childRoles_ -- array of roles which have this one as parent
@@ -77,6 +81,8 @@ Assignment table represents exercise assignment in a group. It holds keys of the
 
 ## RuntimeEnvironment
 
+Stores information about supported environments which can be used for evaluation on workers.
+
 - _name_ -- human readable name of runtime environment
 - _language_ -- language which can be used in this environment
 - _extensions_ -- list of extensions in yaml format
@@ -105,6 +111,8 @@ Assignment table represents exercise assignment in a group. It holds keys of the
 
 ## SolutionFile
 
+Parent of this entity is `UploadedFile`, only added field is solution to which this file is associated.
+
 - _solution_ -- associated solution to which file belongs to
 
 ## SolutionRuntimeConfig
@@ -129,6 +137,8 @@ Assignment table represents exercise assignment in a group. It holds keys of the
 
 ## SubmissionFailure
 
+Logically queue of failed submissions which deserves further attention from administrator. Administrator can then resolve this issue and information about that will be stored too.
+
 - _type_ -- type of failure, can be for example _broker_reject_ or _evaluation_failure_
 - _description_ -- description of failure which was provided by backend
 - _submission_ -- associated submission which failed
@@ -155,6 +165,8 @@ Represents result of one logical test from job configuration.
 
 ## UploadedFile
 
+Entity which represents one file which was uploaded to api server. This entity uses _Single Table Inheritance_ and its children are `ExerciseFile` and `SolutionFile` entities.
+
 - _name_ -- original name of file uploaded to api
 - _localFilePath_ -- destination where file is stored on api server
 - _uploadedAt_ -- datetime of file upload