If I click erase iPhone does it delate all my pictures ?

Everything on your phone will be gone. If you are not using iCloud Photos, then a restore from last backup will bring back the photos if they are included in your backups. If you are using iCloud Photos, then the photos will be downloaded from iCloud back to your device. The same is true for Messages. Refer to these 2 support articles that shows what is backed up in your iCloud backups and how to use iCloud Photos along with Messages in iCloud.

Set up and use iCloud Photos - Apple Support

What does iCloud back up? - Apple Support

crystal 2000 Said:

"If I click erase iPhone does it delate all my pictures ?: I am hesitant in erasing my iPhone, will it delate all my pictures and messages?"

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Perhaps.

Export these First:

If you never create a backup of these photos, then they will be gone. So, create a backup, prior to the reset. Perform as instructed here: Transfer Photos and Videos from your iPhone or iPad to your Mac or PC - Apple Support

If you click Erase......everything.....on the iPhone will be erased, and the phone will look like it did when it was brand new.