There are several types of bidding systems in Google Ads. You can call these as the bidding strategies.
You can find automated and manual bidding types in Google.
In google, you can find that there are twelve different types of bidding types. Here is the list if you want to learn bid strategy
3 Maximize Conversions
5 Maximize Clicks
6 Manual CPC Bidding
7 Target Search Page Location
8 Target Outranking Share
9 CPM Bidding (Cost Per Thousand Impressions)
10 vCPM Bidding (Cost Per Viewable Thousand Impressions)
11 CPV Bidding (Cost Per View)
12 Target Impression Share Bidding
This is a fully automatic bidding strategy.
This can be set at campaign level or portfolio level.
If you want to bring conversion to your website this is the right strategy. Using this target CPA you can optimize your campaign.
Here you can basically set your target CPA and google adjust the CPC to bring more conversion as possible.
In other words, how much you are willing to pay for a conversion.
But this does not guarantee to bring more conversion. Sometimes Google will eat up your money with some low conversions.
ROAS stands for return on ad spend. This is a measurement of the revenue you earn for each dollar you spend for advertising.
ROAS does provide a look at the bigger picture. You can use this bidding strategy to maximize the revenue.
It works best for accounts that have had at least 50 conversions within the past 30 days.
If you have manual CPC bidding you can fully control the bid value. But in enhanced CPC first, you set the bid amount manually at group level or keyword level and enable the ECPC.
You can call this semi automated bidding strategy.
You can have a tight control on keyword level and you allow Google algorithm to change the CPC
Now Goggle uses the AI algorithm to change the bid amount which you will be able to get some conversion. Google may slightly increase or decrease the bid amount based on the algorithm.
I have run several campaigns with ECPC and got some good conversions but unfortunately Google had increased the bid value. So I have never experienced a situation where Google had decreased bid amounts to get a good number of conversions.
How do you test this strategy
Create two identical campaign
Run first one with manual CPC
Run the second one with ECPC
Now you can compare the results and analyse the results. That is how I normally start with enhanced cost per click strategy
You can use the Target Impression Share bidding strategy for border keywords if you want to target a larger audience. (or Top of the funnel)
This is good if you are going to own a space of a particular niche because you target a large audience first.
You can lower your CPC
This is a good testing strategy if you do not have any conversion data on a given domain
How to choose a bid strategy