chore: refine the overview of user guide (GreptimeTeam#1069)

docs/nightly/en/user-guide/overview.md

@@ -48,11 +48,11 @@ Break down the query step by step:
 
 Next, let's analyze the key features of GreptimeDB demonstrated by this query example:
 
-- **Unified Storage:** GreptimeDB stores both time-series metrics and [logs](/user-guide/logs/overview.md) in one database. The simplified architecture and data consistency enhances the ability to analyze and troubleshoot issues, and can lead to cost savings and improved system performance.
+- **Unified Storage:** GreptimeDB is the time series database to store and analyze both metrics and [logs](/user-guide/logs/overview.md). The simplified architecture and data consistency enhances the ability to analyze and troubleshoot issues, and can lead to cost savings and improved system performance.
 - **Unique Data Model:** The unique [data model](/user-guide/concepts/data-model.md) with time index and full-text index greatly improves query performance and has stood the test of large data sets. It not only supports metric [insertion](/user-guide/write-data/overview.md) and [query](/user-guide/query-data/overview.md), but also provides a very friendly way to [write](/user-guide/logs/write-logs.md) and [query](/user-guide/logs/query-logs.md) logs.
 - **Range Queries:** GreptimeDB supports [range queries](/user-guide/query-data/sql#aggregate-data-by-time-window) to evaluate [expressions](/reference/sql/functions/overview.md) over time, providing insights into metric trends. You can also [continuously aggregate](/user-guide/continuous-aggregation/overview) data for further analysis.
 - **SQL and Multiple Protocols:** GreptimeDB uses SQL as the main query language and supports [multiple protocols](/user-guide/clients/overview.md#protocols), which greatly reduces the learning curve and development cost. You can easily migrate from Prometheus or [Influxdb to GreptimeDB](/user-guide/migrate-to-greptimedb/migrate-from-influxdb), or just start with GreptimeDB.
-- **JOIN Operations:** The data model of GreptimeDB's time series tables makes it the first time series database to support [JOIN operations](/reference/sql/join.md).
+- **JOIN Operations:** The data model of GreptimeDB's time series tables enables it to support [JOIN operations](/reference/sql/join.md) on metrics and logs.
 
 Having understood these features, you can now go directly to exploring the features that interest you, or continue reading the next step in the sequence.
 

docs/nightly/zh/user-guide/overview.md

@@ -48,11 +48,11 @@ ALIGN '5s' BY (host) FILL PREV
 
 接下来解析一下该查询示例展示的 GreptimeDB 关键功能：
 
-- **统一存储：** GreptimeDB 将时间序列指标和 [日志](/user-guide/logs/overview.md) 存储在一个数据库中。简化的架构和数据一致性增强了分析和解决问题的能力，并可节省成本且提高系统性能。
+- **统一存储：** GreptimeDB 是支持同时存储和分析指标及[日志](/user-guide/logs/overview.md)的时序数据库。简化的架构和数据一致性增强了分析和解决问题的能力，并可节省成本且提高系统性能。
 - **独特的数据模型：** 独特的[数据模型](/user-guide/concepts/data-model.md)搭配时间索引和全文索引，大大提升了查询性能，并在超大数据集上也经受住了考验。它不仅支持[数据指标的插入](/user-guide/write-data/overview.md)和[查询](/user-guide/query-data/overview.md)，也提供了非常友好的方式便于日志的[写入](/user-guide/logs/write-logs.md)和[查询](/user-guide/logs/query-logs.md)。
 - **范围查询：** GreptimeDB 支持[范围查询](/user-guide/query-data/sql#aggregate-data-by-time-window)来计算一段时间内的[表达式](/reference/sql/functions/overview.md)，从而了解指标趋势。你还可以[持续聚合](/user-guide/continuous-aggregation/overview)数据以进行进一步分析。
 - **SQL 和多种协议：** GreptimeDB 使用 SQL 作为主要查询语言，并支持[多种协议](/user-guide/clients/overview.md#protocols)，大大降低了学习曲线和接入成本。你可以轻松从 Prometheus 或 [Influxdb 迁移](/user-guide/migrate-to-greptimedb/migrate-from-influxdb)至 GreptimeDB，或者从 0 接入 GreptimeDB。
-- **JOIN 操作：** GreptimeDB 的时间序列表的数据模型，使其成为第一个支持[JOIN 操作](/reference/sql/join.md)的时序数据库。
+- **JOIN 操作：** GreptimeDB 的时间序列表的数据模型，使其具备了支持[JOIN](/reference/sql/join.md)数据指标和日志的能力。
 
 了解了这些功能后，你现在可以直接探索感兴趣的功能，或按顺序继续阅读下一步骤。