Basically what it's doing is using the icon for Physick and creating a short 2-step chain of actions, where you cast physick on <t>, which stands for currently selected target, and your pet does the same with Embrace.
You type it in one macro, on three separate lines. For stuff that targets you, you use the term <me>. You can also designate party members by using <p#> where the # is anything from 1 to 8.
Search the official Lodestone site for more macro information. They have a lot of different commands you can throw in to do interesting stuff.
A few final notes; every new action needs to be put on it's own line. Actions that have one word just need to be written exactly as the skill name is displayed, i.e. /ac Physick <t>. Actions with more than one word require quotes around the name of the skill, i.e. /ac "Eye for an Eye" <t>, but otherwise follow the same rules for spelling and needing a separate line of it's own and all that.
If you use the /wait command, the timer uses whole numbers, in seconds. So /wait 5 would work, but /wait 5.5 would not.
Using another macro replaces the last macro used as far as /wait goes. So if you have a macro that you use with a /wait command, and then you use another macro before the first macro finishes, the first macro won't finish.