Iodine is a very powerful antiseptic. It is for example the main component of Betadine.
In general though, iodine is just what thyroid requires to function properly. It's naturally mainly found in sea food. And in the 20th century, most occidental countries began to add it to table salt to stop goiters among the population. Since then, the majority of countries in the world add it to table salt, to cattle feeds and so on...
I agree with Maxx that it's quite hard to be iodine deficient nowadays if you eat average occidental diet. Though certain countries have no iodine salt supplementation but it's quite rare (Lebanon and Israel for ex). Also there are wide differences in the amount of iodine added to salt among countries. Norway adds 5mg/kg, United states and Canada add 76mg/kg... And supplemented salt is not always used.
Certain doctors like David Brownstein advocate that we all are super iodine deficient cause other halogens (particularly fluoride and bromine) are over proliferating in our environment (water, food and salt additives, mattresses and furnitures, treated wood floors...) According to him, those halogens compete with iodine absorption. And he thinks we need way more iodine to get rid of the excess bromine and fluoride that accumulate in our bodies.
His views are seen as controversial in the medical world though so I don't know if he's right or wrong.
Anyway precaution is necessary if someone tries to supplement with iodine, especially lugol cause it's very concentrated.
Some people on internet say it works like magic with many benefits, some say it has triggered thyroid issues with them like subclinical hypothyroidism or auto immune thyroid issues.
I took it cause I was feeling fatigued and I thought my new mattress was making me sleep bad (I still think it's the case). You know this smelly new mattresses that smell petrol and chemicals like shit ?
I didn't take much, I took like 1 drop of Lugol's 5% every week for 2 months approximately. And I have to admit it was very beneficial for me, I felt more energetic, more lively, slept way better, less anxious. But at the end I was feeling like I could get "addicted" to it and would need it more and more. Excess iodine can disrupt the thyroid. So I've just decided to stop it altogether. I make sure I get enough iodine through my diet. I may need to take it again in the future.
My personal stance on iodine is that it's something that helps in a "bad" environment.
In general, I dislike supplements and I have never taken any in my whole life until this iodine. I had an intuition that I needed it and it did was very beneficial for me for the time I used it.
If any wants to try I would just advocate precaution, and never take too much at once.