I am kinda new in this topic and wondering what is the difference between Page Views and Event data type in Google Tag Manager. I would like to create an e-commerce funnel. I have configured tags for every steps in GTM and they work properly in preview mode. But I can't find them in Google Analytics. I've been creating tags with pageview -> some page views tags. Where this type of tags are stored in Google Analytics? Should I change it to event data type? And in which case could we need some pageviews tags otherwise?
GTM and GA are two different systems, that unfortunately use the same words for rather different things.
GTM is a deployment system for Javascript tags. In GTM Parlance, an "event" is something that makes GTM update its internal variables and allows for triggering tags. GTM events manifest themselves as a key with the name "event" in the datalayer (GTM overwrites the "push" method of the datalayer array to detect the "event" key when it is contained in an object that is pushed to the datalayer). A pageview in GTM is just one type of event that happens when the GTM code is first executed. By itself it does not send data anywhere and nothing is stored. Data is sent only by the tags that are configured to be triggered by an event.
GA is a system that records tracking data. Tracking data is sent as "hits", where a hit is a http request with a payload that is formatted according to a certain protocol (the measurement protocol, which can be used in any language that supports http requests, and is also used by the analytics.js library). Hits come in different types (pageview, event, timing, and possibly others). The difference is not so much technical (its all http requests), is that the different hit types are by convention tied to different "dimensions", i.e. descriptive properties of the hit. A "page view" hit has a document location and document title. An "event" in GA has additionally the dimensions "event category", "event action" and "event label". That distinction made sense when GA was created, because back then a "page view" was more or less well defined by browser behaviour, but today with ajax and SPAs and all that it becomes more an more meaningless, which is why GA4, the new version of Google Analytics, now only has one hit type - the event, to which you can add dimensions by way of parameters.
So a page view in GTM maybe configured to send a page view in Google Analytics, but does not have to be; the two things have the same name, but exists independently. If a GTM event is not recorded, then it probably has not GA tag connected to it via a trigger. GTM events by themselves do not store data anywhere.
As for the funnel, in Universal Analytics you would create this by implementing enhanced e-commerce. Enhanced E-Commerce can be implemented both via pageviews or via events (that mostly depends on how your page is structured - if you have a checkout with multiple pages you might want to use page views, if everything happens on one page you would rather use events). The important thing is that the appropriate dimensions and metrics are attached to the hit. In GTM the easiest way to this is to have your developers set up the datalayer structure according to the linked documentation, and then you simply check the "enhanced e-commerce" feature in you GA tag and point it to the e-commerce variable in your datalayer (instructions are in the documentation, if you expand the "See the Tag Configuration for this Example" sections by clicking on them).