If you're looking for an extension to summarize and extract data from a big spreadsheet in Google Sheets, GPT Workspace is a great choice. This productivity tool combines ChatGPT and Gemini to automate processes involving Google Sheets, Docs, Slides, Gmail and Drive. It can categorize, summarize and extract data from spreadsheets, for example, to help you wrangle a big data set. It also works with more than 30 languages and has a free plan with no usage limits, so it's good for a broad audience.
Another option is Neptyne, which marries Python programming code with Google Sheets to let you do more-advanced data processing and analysis. Neptyne can import data from a variety of sources, including CSV files and databases, and can perform tasks like summarization, anomaly detection and time series forecasting. It also has visualization and automation abilities, so it's good for practical uses like predicting stock quotes and weather forecasts.
If you want a more basic, user-friendly interface, Numerous.ai is a good option. This AI plugin for Google Sheets and Excel lets you perform tasks like summarizing and categorizing data, and it's good for digital marketing campaigns and team collaboration. It's also relatively affordable, so it's a good way to get some AI abilities without delving into the world of API keys.