The hashtags used on Google+ work in two ways:
You can click on them (when blue) and they will take you straight to the search, showing posts with the hashtag in question. People who search for a certain topic can do so with or without the # and a keyword: You get slightly different results with either method, I've noticed.
Using hashes is a good way to get your posts noticed by the public in search, not just in photo themes but on any topic, works also in Communities.
Of course that means posting in Public or public communities, otherwise only those with whom the post was shared can see the results (members in your circles or private communities).
So you can use your own unique hashtag (like my #Jaanatip or the more public #Plushelp ) and find them later. You may also share posts only to yourself, your own private community or an empty circle and easily find the posts in the Google+ search.
You may use capital letters in hashtags, it doesn't make any difference in the search, like #GooglePlus #WhatDoYouThink or even use under_scores to connect words. Try to keep the hashes short, preferably under 20 characters. Long hashes have a tendency to stop working, same applies to hashes with special characters, even the +.
One more thing: Twitter hashes don't have a long lifespan but the Google+ hashtags don't usually disappear. A good thing for the search.
Unfortunately the hashes on comments don't come up in the search anymore, just the ones from the main post. But they still work as clickable links.
You can do fun things with the hashes:
Choose a topic and post a series using the same hash with all the posts coming up in the search.
Example: #Jaana100 or 100 ways to be happy!
Is there a popular hashtag I can use in a post?
When you start typing after the # Google suggests hashtags to you depending on what you type. You can leave a post without hashtags and sometimes Google will add them for you.
But I think it's best to create your own:
It all depends on the topic of your post. If it's about politics, science, sports, nature, photography...
- All those words can be hashtags by typing the # first.
Then they come up in searches and are also clickable links that take you to the search on Google+ with lots more posts about that topic.
Don't use hashes that have nothing to do with the post... Don't overuse them either.
One line of hashtags at the end of the post is the maximum recommended amount. Sometimes we see photo posts with 20 - 50 hashes and nothing else, no explanation or where the photo was taken. I never +1 those or even comment on the posts, they annoy me. Talk about spoiling the visual pleasure that is the image.
You can also make your own unique hashtag that you put in your posts, like my #JaanaTravel .
Hashtags now show Google+ posts in Google search:
Learn more about the hashtags:
Here's a nice use for hashes: A "Timeline" of my posts with the hashtag "jaanatip" at the end:
To get yours just replace my G+ ID and the hashtag with your own.
If you get a blank page, the Google API's have been used, try again tomorrow.
What is the point of Hashtags