Welcome to Salesforce Summer 18 Sandbox Preview is released on 24th April 2018. Salesforce launched its Summer 18 logo as Snorkel Codey.

Looking for the Summer18 Salesforce pre-release account ??? Click over here
They are many more exciting features available in Salesforce Summer 18. Look out below for them.

Lightning Blot Solutions

Create new Lightning Blot Solutions for users. it supports for

• Custom Apps
• Flow Categories
• Community Templates

Lightning Usage App

It lightning Usage org under lightning Experience and Salesforce Mobile, you can find Key Metrics like Monthly active Users visited, Daily users with help of reports and you find monthly and daily active users based on their profiles.
We can track the most viewed custom lightning pages, Most viewed page in the last 7 days
We can track how many total switches and unique switches happen in org and we can filter them by last monthly.

on click on Run Lightning Optimizer, it will open the below image and

and allow popup

Reports UI :

UI of Reports is Changed into LEX.

Dashboards :

DashBoards Ui is changed into LEX. After Saving Dashboard Subscribe Button. On click on Button, you can subscribe to that report based on a daily, monthly, week or any required day of the week at a particular time. you can schedule the dashboard to send mail to you or any other who required to see dashboard status.

Now we can share Filtered URL with others
New URL Format for Lightning Experience and the Salesforce Mobile App
Here are some examples of the new format.

Previous format: https:///one/one.app/#/sObject/Account/home
New format: https:///lightning/o/Account/home

• Object Home page

Previous format: https:///one/one.app#/sObject/006R000000245p1IAA/view
New format: https:///lightning/r/Opportunity/006R000000245p1IAA/view

• Record page

See how /lightning has replaced /one/one.app? Existing URLs that use /one/one.app

Search the Object You Want Easily from Anywhere

Get a component reference from your org by adding /componentReference/suite.app to know the usage of component and code reference from your org.
Ex: https://geoapp-dev-ed.lightning.force.com/componentReference/suite.app
Rename Your My Domain When You Want: If you have an existing My Domain subdomain, you can now rename it without contacting Salesforce Customer Support. My Domain lets you highlight your brand, so Salesforce is making it easier to change it when your company’s name or branding changes.

Implement lightning:isUrlAddressible in your components to generate a pageReference that you can use to open components in a tab or subtab.

and many more check out here for more information. Salesforce offers PDF and HTML versions.

List out the below Key Dates for Salesforce Summer 18 Sandbox preview Release

Learn more about Set Up Two-Factor Authentication in Salesforce