What is this psuedo-JSON in my WP database and how to I alter it?

I'm working on a large Wordpress migration and, somehow, the previous installation had allowed for non-web-friendly filenames. I'm using javascript (because that's what I know best) to write a script that will look through the tables, find problematic filenames, change them in the database, and then change the actual filename. No problem.

But, some of the files are referenced in some kind of stringified JSON that I don't recognize. For instance:

meta_value: 'a:5:{s:5:"width";i:1044;s:6:"height";i:864;s:4:"file";s:42:"2015/02/The-Impact-of-CAPL-work_2017_1.jpg";s:5:"sizes";a:5:{s:9:"thumbnail";a:4:{s:4:"file";s:42:"The-Impact-of-CAPL-work_2017_1-150x150.jpg";s:5:"width";i:150;s:6:"height";i:150;s:9:"mime-type";s:10:"image/jpeg";}s:6:"medium";a:4:{s:4:"file";s:42:"The-Impact-of-CAPL-work_2017_1-300x248.jpg";s:5:"width";i:300;s:6:"height";i:248;s:9:"mime-type";s:10:"image/jpeg";}s:12:"medium_large";a:4:{s:4:"file";s:42:"The-Impact-of-CAPL-work_2017_1-768x636.jpg";s:5:"width";i:768;s:6:"height";i:636;s:9:"mime-type";s:10:"image/jpeg";}s:5:"large";a:4:{s:4:"file";s:43:"The-Impact-of-CAPL-work_2017_1-1024x847.jpg";s:5:"width";i:1024;s:6:"height";i:847;s:9:"mime-type";s:10:"image/jpeg";}s:32:"twentyseventeen-thumbnail-avatar";a:4:{s:4:"file";s:42:"The-Impact-of-CAPL-work_2017_1-100x100.jpg";s:5:"width";i:100;s:6:"height";i:100;s:9:"mime-type";s:10:"image/jpeg";}}s:10:"image_meta";a:12:{s:8:"aperture";s:1:"0";s:6:"credit";s:0:"";s:6:"camera";s:0:"";s:7:"caption";s:0:"";s:17:"created_timestamp";s:1:"0";s:9:"copyright";s:0:"";s:12:"focal_length";s:1:"0";s:3:"iso";s:1:"0";s:13:"shutter_speed";s:1:"0";s:5:"title";s:0:"";s:11:"orientation";s:1:"0";s:8:"keywords";a:0:{}}}'

Is this some wordpress thing? Or a kind of mysql-friendly stringification? How can I safely parse & update it?