2. Data Modeling

https://trailhead.salesforce.com/data_modeling/objects_intro

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Overview of Objects

Identify Field

Force.com automatically assigns an identity field (called ID) to every object, and manages the identity data in every record. This identity field usually comes in a 15-character case sensitive form, which you may have already seen while using the platform

System Fields

CreatedDate - the Date and time when the object was created

CreatedById - the ID of the User who created the object

LastModifiedById - the ID of the User who last modified the object

LastModifiedDate - the date and time when the object was last modified by a user

SystemModStamp - the date and time when the object was last modified by a user or process, such as a trigger

Name Field

A name can be one of two types - a text string or an auto-number field

Custom Fields

Auto Number 

a system-generated read-only sequence number, analogous to the SQL identity type. These fields can be used to provide a unique ID that is independent of the internal object ID. These fields are not used in creating object relationships

Checkbox

for representing Boolean data.

Date or Date/Time

for representing dates or date and time combinations.

Number

for representing real numbers, with optional decimal points

Email, Phone and URL

format-validated email, phone and URL string representations.

Picklist and Multi-Select Picklists

represent values from a list.

Text and Text Areas

for representing text of various lengths.

Currency

a formatted number type, with optional multi-currency support.

Formula

a read-only field holding data generated from a formula expression.

Geolocation

allows you to identify locations by their latitude and longitude and calculate distances between locations.

Other Features of Objects

Formulas

Formulas can be used in many places, such as setting up validation rules, creating workflow rule criteria, and even to define a field

The formula language is a rich expression language that lets you perform calculations and manipulate strings, dates, numbers and regular expressions

Validation

Validation rules help improve data quality by preventing users from saving incorrect data. These rules use the same formula syntax as found in formula field types to define a formula which is evaluated each time a record is saved. If the formula for a validation rule evaluates as “True”, the save is aborted and an error message displayed

Triggers

Triggers, written in the Apex language, are pieces of code that can fire before or after a record is saved, updated or deleted

Labels

Every object and record has a label and can include a description, for help, which is automatically included in the user interface

Notes and Attachments

You can create, view, and edit notes and add attachments for any record in an object that has this functionality enabled. This provides users of the object the ability to easily add arbitrary text notes, and upload associated documents, for each record.

Track Field History

Certain fields on your objects can be configured to track their history. Any time a user modifies any of the field data whose history is set to be tracked, a new entry is added to an automatically created History related list. This History list tracks the date, time, nature of the change, and who made the change.

Security

Database services provide a flexible security model that you can use to control who has access to objects, records and/or fields.