A CSV (Comma-Separated Values) file is a plain text file that stores tabular data (numbers and text) in plain-text form, with each line representing a data record and each field within the record separated by a comma.

XML is a markup language that defines a set of rules for encoding documents in a format that is both human-readable and machine-readable. It is often used for structuring, storing, and transporting data.

GeoJSON is an open standard format designed for representing simple geographic features along with their non-spatial attributes. It's based on JavaScript Object Notation (JSON).

A Shapefile is a widely-used geospatial vector data format for geographic information system (GIS) software. It consists of a set of files with the same base name but different extensions.

In ArcGIS: You can add a CSV file to ArcMap by selecting "Add Data" and choosing the CSV file. ArcGIS will automatically recognize the file's structure and display it as a table. You can join this table with spatial data based on common attributes.
In QGIS: Use the "Add Delimited Text Layer" tool to import CSV data. Specify the delimiter and choose the geometry columns. QGIS will create a point layer based on the specified X and Y fields.

In ArcGIS: XML files may be used for metadata or data interchange. You can import XML metadata in ArcCatalog, and XML-based data can be converted to other formats using geoprocessing tools.
In QGIS: XML files might be used for styling information or as part of data interchange. QGIS supports the import of XML-based styles, and plugins may be available for converting XML-based data to compatible formats.

In ArcGIS: GeoJSON files can be added to ArcMap using the "JSON To Features" geoprocessing tool. It converts GeoJSON features to a feature class.
In QGIS: Simply drag and drop a GeoJSON file into the QGIS interface, and it will be added as a layer. QGIS natively supports GeoJSON.

In ArcGIS: Shapefiles can be added directly to ArcMap or ArcCatalog. They consist of multiple files (.shp, .shx, .dbf, etc.) that should be kept together in the same folder.
In QGIS: Shapefiles can be added by dragging and dropping the .shp file into QGIS or by using the "Add Vector Layer" tool. QGIS natively supports Shapefiles.