What is the GET parameter?
getParameter() is a URL parameter that is used when a client aka a browser sends a request to a site’s server. In response, the server sends all the files to the browser and a person can finally see the page.
This communication (data exchange: request and response) happens via the HTTP protocol.
GET URLs parameters in use
HTTP GET parameters look like pairs of names and their certain values after the ? sign. The names and their values are separated by the = sign.
Multiple parameters are separated using a & sign.
Example: http://example.com.html/?name1=value1&name2=value2 
The main use cases are the following:
- Faceted navigation (for filtering and sorting content). Example: ?color=blue is used to browse only blue items.
- Tracking of Session IDs and website traffic with UTM parameters. Example: ?utm_medium=cpc is used to identify what cost-per-click type of link was used.
Each request made with the HTTP GET request parameters method can be stored in the cache, browser history, or as a bookmark. The Get.request parameter is mainly used to get data, limited only by the maximum length of the URL.
It’s worth saying that URL GET parameters are less secure, unlike POST methods. When information retrieval is performed with a mechanism that constructs a target URL from user-provided information, such as the query fields of a form using GET, potentially sensitive data might be provided that would not be appropriate for disclosure within a URL. That’s why GET parameters are not suitable for handling sensitive data.
So, it is advisable to only use the GET parameter to request files that are not security-relevant, as the data is transmitted via the URL.
What are the GET parameters’ SEO implications?
Because of the generated dynamic URLs, duplicate content may appear on a site. It will negatively affect your pages’ rankings. It is advisable to use canonical tags for these URLs.
Another issue that you may face when using the GET URL parameter is the poor readability of the URL. Too many parameters within a URL can make it illegible and hard to remember. The problem can be solved with redirection to the shorter variants of the URL.