Why is there the thin client if the thick client can work in the managed mode?
Indeed, both the thin client and the thick client can work with applied solutions running in managed application mode. And both clients can work directly with file infobases and connect to a 1C:Enterprise 8 server cluster over LAN or TCP/IP.
But they do have different capabilities in how they connect to infobases. The thin client provides connection to infobases using HTTP and HTTPS protocols through a web server. In other words, a thin client can connect users who are working online, over the Internet.
In comparison to the thick client, the thin client requires less hardware resources and is provided as a separate, smaller distribution kit. This small distribution kit can be transferred to a remote user, then he or she can install it independently and connect to the infobase.
The thin client supports regular user work scenarios.
The thick client is intended mostly for administrators and developers to work in Designer mode (where they can perform administrative actions or modify the applied solution).
You might also need the thick client for backward compatibility with applied solutions created in earlier platform versions. This is the case if an application has not been adjusted for use in managed application mode or has been adjusted only partially, which requires the use of both ordinary and managed forms.
Why is there the thin client if there is the web client?
At first glance it may seem that the existence of a web client would make a thin client unnecessary. The reason for this is that the web client’s features are identical to the thin client's, and there is no need to install it on a user's PC.
This is not the case, however. Although the web client does not need to be installed and therefore might seem easier to use, the thin client does still offer some essential advantages.
First, from a functional point of view, a web client cannot do everything that a thin client can. The amount of such extra functionality is not large, and most off-the-shelf applications are implemented for use with both thin and web clients. However, some specialized applications may utilize functionality which is only partially implemented in a web client or not implemented at all. For example, interacting with file systems, working with XML, working with email, and so on.
Second, a web client can only connect to infobases through a web server, and this might not meet the data security requirements. For example, an organization might not want to expose the web server, but still would like to work over VPN with remote clients.
Third, there are differences in licensing. The web client can use the server client license only. This means that the client license key must be installed on the 1C:Enterprise server. Unlike the web client, however, the thin client can use client licenses installed on the server as well as client licences installed on the client computer.