You cannot explore Pinterest when you are offline. You need the Internet to do so. Pinterest is an online photo-sharing social network. However, you can save images on your device, and this will be available on your device (camera roll or your gallery) even when you are offline.
To save images for offline view:
First, open the Pinterest app, find whatever you wish to save, click the three vertical dots on the lower left side of your screen that is below the image.
You will see three options: save the image, copy link, and report. Click the save image option, and the image will be saved to your device. You can access this even if you do not have access to the Internet.
There are instances when you would like to see some of the things that you have saved on Pinterest offline. You cannot access Pinterest when you are offline, but you can definitely check the pins that you have downloaded from Pinterest on your phone.
The items that you have saved on your board cannot be opened when you are offline, but if you would click download, they would automatically become available on your phone. There are three vertical dots that you will see on the lower left side of your screen that can be clicked below the left side portion of the screen. Click the save image option. The saved image can then be accessed whether or not.