How many of you noticed "Did you mean " feature appears right below after SharePoint search. I was just curious to know how the SharePoint implements this feature. Let's see the findings below.
There are two types of Query spelling suggestions.

Dynamic - The query spelling correction uses the content-aligned dictionary.
Static - The query spelling correction uses the out of the box static spelling dictionaries features.

You can configure the dictionary mode using the following PowerShell command

$ssa = Get-SPEnterpriseSearchServiceApplication
Get-SPEnterpriseSearchQuerySpellingCorrection -SearchApplication $ssa
Set-SPEnterpriseSearchQuerySpellingCorrection -SearchApplication $ssa -SpellingDictionary Static