docs: align project description (#1064)

Signed-off-by: tison <wander4096@gmail.com>

Author: tisonkun

docs/nightly/en/index.md

@@ -4,20 +4,18 @@
     <img src="/logo-greptimedb.png" alt="GreptimeDB Logo" width="400">
 </p>
 
-GreptimeDB is an open-source time-series database focusing on efficiency, scalability, and analytical capabilities.
-It's designed to work on infrastructure of the cloud era, and users benefit from its elasticity and commodity storage.
+**GreptimeDB** is an open-source unified time-series database for **Metrics**, **Events**, and **Logs** (also **Traces** in plan). You can gain real-time insights from Edge to Cloud at any scale.
 
-GreptimeDB is also on cloud as
-[GreptimeCloud](https://greptime.com/product/cloud), a fully-managed time-series
-database service that features serverless scalability, seamless integration with
-ecoystem and improved Prometheus compatibility.
+GreptimeDB is also on cloud as [GreptimeCloud](https://greptime.com/product/cloud),
+a fully-managed time-series database service that features serverless scalability,
+seamless integration with ecoystem and improved Prometheus compatibility.
 
 Our core developers have been building time-series data platforms for years. Based on their best-practices, GreptimeDB is born to give you:
 
+- Unified all kinds of time series; GreptimeDB treats all time series as contextual events with timestamp, and thus unifies the processing of metrics and events. It supports analyzing metrics and events with SQL and PromQL, and doing streaming with continuous aggregation.
 - Optimized columnar layout for handling time-series data; compacted, compressed, and stored on various storage backends, particularly cloud object storage with 50x cost efficiency.
 - Fully open-source distributed cluster architecture that harnesses the power of cloud-native elastic computing resources.
 - Seamless scalability from a standalone binary at edge to a robust, highly available distributed cluster in cloud, with a transparent experience for both developers and administrators.
-- Native SQL and PromQL for queries, and Python scripting to facilitate complex analytical tasks.
 - Flexible indexing capabilities and distributed, parallel-processing query engine, tackling high cardinality issues down.
 - Widely adopted database protocols and APIs, including MySQL, PostgreSQL, and Prometheus Remote Storage, etc.
 - Schemaless writing that automatically creates tables for data.

docs/nightly/zh/index.md

@@ -4,17 +4,17 @@
     <img src="/logo-greptimedb.png" alt="GreptimeDB Logo" width="400">
 </p>
 
-GreptimeDB 是开源的时序数据库，注重效率、可扩展性和分析能力。GreptimeDB 可以在云时代的基础设施上工作，使用户受益于良好的灵活性和高性价比的存储。
+GreptimeDB 是开源的统一时序数据库，能同时处理**指标**（Metrics）、**事件**（Events）、**日志**（Logs）和**追踪**（Traces）。从云到端，GreptimeDB 能从任意规模的时序数据中获取实时数据洞察。
 
 GreptimeDB 经由 [GreptimeCloud](https://greptime.cn/product/cloud) 提供云服务。
 GreptimeCloud 是一个完全托管的时序数据库服务，具有无服务器的可扩展性、与生态系统的无缝集成和 Prometheus 兼容性。
 
 我们的核心开发人员多年深耕于建立时序数据平台。基于他们的丰富经验，GreptimeDB 应运而生，并为用户提供：
 
+- 统一的时序数据处理；GreptimeDB 将所有时序数据统一抽象成带有时间戳和上下文的事件，从而统一了指标和事件的存储和分析。同时，GreptimeDB 支持使用 SQL 和 PromQL 进行分析，以及通过持续聚合能力来实现流处理。
 - 为处理时序数据而优化的列式布局；经过压缩、整理，并存储在各种存储后端，尤其是可以节省 50 倍成本效率的云对象存储。
 - 完全开源的分布式集群架构，利用云原生弹性计算资源的强大功能。
 - 从边缘节点的单机部署到云端强大、高可用的分布式集群的无缝扩展，为开发人员和管理员提供透明的体验。
-- 原生 SQL 和 PromQL 的查询支持，以及便于复杂的分析任务的 Python 脚本。
 - 灵活的索引功能和分布式、并行处理查询引擎，解决高基数的问题。
 - 适配广泛采用的数据库协议和 API，包括 MySQL、PostgreSQL 和 Prometheus 远程存储等。
 - Schemaless 写入，自动为数据创建表格。