A dataset is a "set of data", for example, it would be the data of a sample, or the data of a finite population. Besides, a dataset could be an article or report which analyses a set of data.

Dataset is a collection of similar and related data for processing by computer. However,there are other definitions of dataset. In the field of Mahtematics, dataset provide an efficient and logical collection of data that can be easily accessed using AutoMate expressions. Using the Loop Dataset action makes traversing a dataset simple, while the use of expressions with specific column numbers makes accessing any row of a dataset a snap. 

Another definition is dataset is a collection of data.

A dataset is a "set of data", for example, it would be the data of a sample, or the data of a finite population. Besides, a dataset could be an article or report which analyses a set of data.

In "everyday language" a dataset is simply a set of data, that is, a collection of observations, recordings, measurements (like Jorge and Mariano explained).

I a more specific use, dataset means all the data belonging to one particular observational unit. For instance is this unit is a human being, the data set may contain data about the body weight, height, age, blood pressure, hair color, education, etc. of a given person. If the unit is a company, the data set may contain data about the number of employees, the sales, cash-flow, shares value, organization structure etc.

A collection of such data sets makes up a data table. Data tables are often presented really in a table-like layout, with one data set per row. This way each column of the data table refers to a particular variable (like age, bloodpressure, sales, ...).

https://en.wikipedia.org/wiki/Data_set

Oh dear colleagues thank you all, but I know that. My question is about the terminology on Researchgate:  for example: in home page, you find a notification saying " Jochen Wilheim added a dataset". When you open to read, you find an article.

I did not add any dataset; RG did it ;)

I don't know what RG means with "dataset". I would suspect that is means "some stuff related to some of one's reasearch work" and it could be a publication, a paper, a poster, a file containing data, a supplement to a paper, anything like that. I don't think that this is used as a technical term with a very precise meaning (expect in the common way as "a collection of data", since written words, pictures, tables etc. are all "data", and this data is "collected" in (and provides as) a particular computer file).

hahaha, I take your name as just example :)