In simple words,
Server pushes messages to client without client request [
as asp.net is web based technology server send response only when client request for it], SingnalR provides a simple ASP.NET API for creating server-to-client remote procedure calls (RPC) that calls JavaScript functions in client browsers from server-side .NET code. basically it transfer Non-compressed JSON text or plain text.
SignalR is an open-source .NET library for building web applications that require live user interaction or real-time data updates.
see below links for detail
Tutorial: Getting Started with SignalR 2 | The ASP.NET Site[
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SignalR Getting Started | The ASP.NET Site[
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